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Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	GARTNER INC
Entity Central Index Key	0000749251
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		89,711,737
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 11,675,031,229

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 156,368	$ 538,908
Fees receivable, net of allowances of $7,700 and $12,700, respectively	1,255,118	1,176,843
Deferred commissions	235,016	205,260
Prepaid expenses and other current assets	165,237	124,632
Assets held-for-sale	0	542,965
Total current assets	1,811,739	2,588,608
Property, equipment and leasehold improvements, net	267,665	221,507
Goodwill	2,923,136	2,987,294
Intangible assets, net	1,042,565	1,292,022
Other assets	156,369	193,742
Total Assets	6,201,474	7,283,173
Current liabilities:
Accounts payable and accrued liabilities	710,113	666,821
Deferred revenues	1,745,244	1,630,198
Current portion of long-term debt	165,578	379,721
Liabilities held-for-sale	0	145,845
Total current liabilities	2,620,935	2,822,585
Long-term debt, net of deferred financing fees	2,116,109	2,899,124
Other liabilities	613,673	577,999
Total Liabilities	5,350,717	6,299,708
Preferred stock:
$.01 par value, authorized 5,000,000 shares; none issued or outstanding	0	0
Common stock:
$.0005 par value, 250,000,000 shares authorized; 163,602,067 shares issued for both periods	82	82
Additional paid-in capital	1,823,710	1,761,383
Accumulated other comprehensive (loss) income, net	(39,867)	1,508
Accumulated earnings	1,755,432	1,647,284
Treasury stock, at cost, 73,899,977 and 72,779,205 common shares, respectively	(2,688,600)	(2,426,792)
Total Stockholders’ Equity	850,757	983,465
Total Liabilities and Stockholders’ Equity	$ 6,201,474	$ 7,283,173

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Fees receivable, allowances	$ 7,700	$ 12,700
Preferred stock par value (in Dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock par value (in Dollars per share)	$ 0.0005	$ 0.0005
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	163,602,067	156,234,415
Treasury stock, Shares	73,899,977	72,779,205

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Total revenues	$ 3,975,454	$ 3,311,494	$ 2,444,540
Costs and expenses:
Cost of services and product development	1,468,800	1,320,198	945,648
Selling, general and administrative	1,884,141	1,599,004	1,089,184
Depreciation	68,592	63,897	37,172
Amortization of intangibles	187,009	176,274	24,797
Acquisition and integration charges	107,197	158,450	42,598
Total costs and expenses	3,715,739	3,317,823	2,139,399
Operating income (loss)	259,715	(6,329)	305,141
Interest income	2,566	3,011	2,449
Interest expense	(126,774)	(127,947)	(27,565)
Gain from divested operations	45,447	0	0
Other income, net	167	3,448	8,406
Income (loss) before income taxes	181,121	(127,817)	288,431
Provision (benefit) for income taxes	58,665	(131,096)	94,849
Net income	$ 122,456	$ 3,279	$ 193,582
Net income per share:
Basic (in dollars per share)	$ 1.35	$ 0.04	$ 2.34
Diluted (in dollars per share)	$ 1.33	$ 0.04	$ 2.31
Weighted average shares outstanding:
Basic (in shares)	90,827	88,466	82,571
Diluted (in shares)	92,122	89,790	83,820
Research
Revenues:
Total revenues	$ 3,105,764	$ 2,471,280	$ 1,857,001
Conferences
Revenues:
Total revenues	410,461	337,903	268,605
Consulting
Revenues:
Total revenues	353,667	327,661	318,934
Other
Revenues:
Total revenues	$ 105,562	$ 174,650	$ 0

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 122,456	$ 3,279	$ 193,582
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments	(31,245)	47,363	(5,986)
Interest rate swaps - net change in deferred gain or loss	(10,844)	3,892	1,670
Pension plans - net change in deferred actuarial loss	123	(64)	(965)
Other comprehensive (loss) income, net of tax	(41,966)	51,191	(5,281)
Comprehensive income	$ 80,490	$ 54,470	$ 188,301

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income, Net	Accumulated Earnings	Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU \| ASU 2016-09	$ (261)				$ (261)
Beginning Balance at Dec. 31, 2015	(132,400)	$ 78	$ 818,546	$ (44,402)	1,450,684	$ (2,357,306)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	193,582				193,582
Other comprehensive income (loss)	(5,281)			(5,281)
Issuances under stock plans	10,339		(2,080)			12,419
Common share repurchases	(51,762)					(51,762)
Stock-based compensation expense	46,661		46,661
Ending Balance at Dec. 31, 2016	60,878	78	863,127	(49,683)	1,644,005	(2,396,649)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,279				3,279
Other comprehensive income (loss)	51,191			51,191
Issuances under stock plans and for acquisition	830,446	4	819,313			11,129
Common share repurchases	(41,272)					(41,272)
Stock-based compensation expense	78,943		78,943
Ending Balance at Dec. 31, 2017	983,465	82	1,761,383	1,508	1,647,284	(2,426,792)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU \| ASU 2018-02				591	(591)
Adoption of ASU \| ASU 2016-16	(13,717)				(13,717)
Net income	122,456				122,456
Other comprehensive income (loss)	(41,966)			(41,966)
Issuances under stock plans	10,181		(3,845)			14,026
Common share repurchases	(275,834)					(275,834)
Stock-based compensation expense	66,172		66,172
Ending Balance at Dec. 31, 2018	$ 850,757	$ 82	$ 1,823,710	$ (39,867)	$ 1,755,432	$ (2,688,600)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income	$ 122,456	$ 3,279	$ 193,582
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	255,601	240,171	61,969
Stock-based compensation expense	66,172	78,943	46,661
Deferred taxes	1,524	(217,414)	(2,648)
Gain on extinguishment of debt	0	0	(2,500)
Gain from divested operations	(45,447)	0	0
Amortization and write-off of deferred financing fees	13,815	15,062	3,082
Changes in assets and liabilities, net of acquisitions and divestitures:
Fees receivable, net	(115,003)	(368,516)	(68,661)
Deferred commissions	(31,247)	(61,393)	(18,673)
Prepaid expenses and other current assets	(50,551)	13,251	(21,604)
Other assets	11,456	(18,529)	20,005
Deferred revenues	187,147	382,852	97,979
Accounts payable, accrued, and other liabilities	55,235	186,811	56,440
Cash provided by operating activities	471,158	254,517	365,632
Investing activities:
Additions to property, equipment and leasehold improvements	(126,873)	(110,765)	(49,863)
Acquisitions - cash paid (net of cash acquired)	(15,855)	(2,641,780)	(48,196)
Divestitures - cash received (net of cash transferred)	526,779	0	0
Cash provided by (used in) in investing activities	384,051	(2,752,545)	(98,059)
Financing activities:
Proceeds from employee stock purchase plan	14,689	11,711	9,250
Proceeds from borrowings	0	3,025,000	715,000
Payments for deferred financing fees	0	(51,171)	(4,975)
Payments on borrowings	(1,010,972)	(404,438)	(835,000)
Purchases of treasury stock	(260,832)	(41,272)	(58,961)
Cash (used in) provided by financing activities	(1,257,115)	2,539,830	(174,686)
Net (decrease) increase in cash and cash equivalents and restricted cash	(401,906)	41,802	92,887
Effects of exchange rates on cash and cash equivalents and restricted cash	(6,489)	25,902	(5,640)
Cash and cash equivalents and restricted cash, beginning of period	567,058	499,354	412,107
Cash and cash equivalents and restricted cash, end of period	158,663	567,058	499,354
Cash paid during the period for:
Interest	117,500	98,500	23,400
Income taxes, net of refunds received	$ 95,800	$ 76,100	$ 86,300

Business and Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES

Business. Gartner, Inc. (NYSE: IT) is the world’s leading research and advisory company and a member of the S&P 500. We equip business leaders with indispensable insights, advice and tools to achieve their goals and build the successful organizations of tomorrow. We believe we have an unmatched combination of expert-led, practitioner-sourced and data-driven research that steers clients toward the right decisions on the issues that matter most. We’re a trusted advisor and an objective resource for more than 15,000 organizations in more than 100 countries — across all major functions, in every industry and enterprise size.

Segments. Gartner currently delivers its products and services globally through three business segments: Research, Conferences (formerly called Events) and Consulting. Our revenues by business segment are discussed below under the heading "Adoption of new accounting standards." When used in these notes, the terms “Gartner,” “Company,” “we,” “us” or “our” refer to Gartner, Inc. and its consolidated subsidiaries.

During 2018, the Company divested all three of the non-core businesses that comprised its Other segment, each of which were acquired as part of the acquisition of CEB Inc. in April 2017. As a result of these divestitures and the movement of a small residual product in the Other segment into the Research business, the Company is no longer recording any additional operating activity in the Other segment effective September 1, 2018. Additional information regarding the divestitures is included in Note 2 –Acquisitions and Divestitures.

Basis of presentation. The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”), as defined in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 270 for financial information and with the applicable instructions of U.S. Securities and Exchange Commission (“SEC”) Regulation S-X. The fiscal year of Gartner is the twelve-month period from January 1 through December 31. All references to 2018, 2017 and 2016 herein refer to the fiscal year unless otherwise indicated.

Principles of consolidation. The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances have been eliminated.

Use of estimates. The preparation of the accompanying consolidated financial statements requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Such estimates include the valuation of fees receivable, goodwill, intangible assets and other long-lived assets, as well as tax accruals and other liabilities. In addition, estimates are used in revenue recognition, income tax expense or benefit, performance-based compensation charges, depreciation and amortization. Management believes its use of estimates in the accompanying consolidated financial statements to be reasonable.

Management continually evaluates and revises its estimates using historical experience and other factors, including the general economic environment and actions it may take in the future. Management adjusts these estimates when facts and circumstances dictate. However, these estimates may involve significant uncertainties and judgments and cannot be determined with precision. In addition, these estimates are based on management’s best judgment at a point in time. As a result, differences between our estimates and actual results could be material and would be reflected in the Company’s consolidated financial statements in future periods.

Business acquisitions. The Company had business acquisitions in both 2017 and 2016 and information related to those acquisitions is included in Note 2 – Acquisitions and Divestitures. The Company accounts for business acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic 805, Business Combinations. The acquisition method of accounting requires the Company to record the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, with any excess of the consideration transferred over the estimated fair value of the net assets acquired, including identifiable intangible assets, to be recorded to goodwill. Under the acquisition method, the operating results of acquired companies are included in the Company's consolidated financial statements beginning on the date of acquisition.

The determination of the fair values of intangible and other assets acquired in acquisitions requires management judgment and the consideration of a number of factors, significant among them the historical financial performance of the acquired businesses and projected performance, estimates surrounding customer turnover, as well as assumptions regarding the level of competition and the cost to reproduce certain assets. Establishing the useful lives of the intangible assets also requires management judgment and the evaluation of a number of factors, among them the expected use of the asset, historical client retention rates, consumer awareness and trade name history, as well as any contractual provisions that could limit or extend an asset's useful life.

The Company classifies charges that are directly-related to its acquisitions in the line Acquisition and integration charges in the Consolidated Statements of Operations. The Company recorded $107.2 million, $158.5 million and $42.6 million of such charges in 2018, 2017 and 2016, respectively. Information related to those charges is included in Note 2 – Acquisitions and Divestitures.

Revenue recognition. On January 1, 2018, the Company adopted Accounting Standards Update ("ASU") No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments required changes in our revenue recognition policies as well as enhanced disclosures. The Company adopted ASU No. 2014-09 using the modified retrospective method of adoption. Under this method of adoption, the cumulative effect of applying the new standard is recorded at the date of initial application, with no restatement of the comparative prior periods presented. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. Prior to January 1, 2018, the Company recognized revenue in accordance with then-existing U.S. GAAP and SEC Staff Accounting Bulletin No. 104, "Revenue Recognition" (“prior GAAP”). Under both ASU No. 2014-09 and prior GAAP, revenue can only be recognized when all of the required criteria are met. Information regarding our adoption of ASU No. 2014-09 and its impact on the Company's consolidated financial statements and related disclosures is provided below under the heading "Adoption of new accounting standards."

Allowance for losses. The Company maintains an allowance for losses that is comprised of a bad debt allowance and, through December 31, 2017, a revenue reserve. Because the adoption of ASU No. 2014-09 on January 1, 2018 discussed above affected the allowance for losses, information regarding the allowance is provided below under the heading "Adoption of new accounting standards."

Cost of services and product development (“COS”). COS expense includes the direct costs incurred in the creation and delivery of our products and services. These costs primarily relate to personnel.

Selling, general and administrative (“SG&A”). SG&A expense includes direct and indirect selling costs, general and administrative costs, and charges against earnings related to uncollectible accounts.

Commission expense. The Company records deferred commissions upon the signing of customer contracts and amortizes the deferred amount as commission expense over a period that considers various relevant factors. Commission expense is included in SG&A expense in the Consolidated Statements of Operations. Additional information regarding deferred commissions and the amortization of such costs is provided below under the heading "Adoption of new accounting standards."

Stock-based compensation expense. The Company accounts for stock-based compensation awards in accordance with FASB ASC Topics 505 and 718 and SEC Staff Accounting Bulletins No. 107 and No. 110. Stock-based compensation expense for equity awards is based on the fair value of the award on the date of grant. The Company recognizes stock-based compensation expense over the period that the related service is performed, which is generally the same as the vesting period of the underlying award. During 2018, 2017 and 2016, the Company recognized $66.2 million, $78.9 million and $46.7 million, respectively, of stock-based compensation expense.

Effective January 1, 2016, the Company adopted ASU No. 2016-09, "Improvements to Employee Share-Based Payment Accounting" ("ASU No. 2016-09"), which mandated certain changes in accounting for stock-based compensation. Among other things, ASU No. 2016-09 permits companies to make an entity-wide accounting policy election to recognize forfeitures of share-based compensation awards as they occur or make an estimate by applying a forfeiture rate each quarter. The Company previously estimated forfeitures but elected to change its accounting policy and account for forfeitures as they occur. ASU No. 2016-09 requires this change in accounting policy to be applied using a cumulative effect adjustment to accumulated earnings as of the beginning of the period in which the rule is adopted. Accordingly, the Company recorded a $0.3 million decrease to its opening accumulated earnings effective January 1, 2016.

Income taxes. The Company uses the asset and liability method of accounting for income taxes. We estimate our income taxes in each of the jurisdictions where we operate. This process involves estimating our current tax expense or benefit together with assessing temporary differences resulting from differing treatment of items for tax and accounting purposes. These differences result in deferred tax assets and liabilities, which are included in our consolidated balance sheets. When assessing the realizability of deferred tax assets, we consider if it is more likely than not that some or all of the deferred tax assets will not be realized. In making this assessment, we consider the availability of loss carryforwards, projected reversals of deferred tax liabilities, projected future taxable income, and ongoing prudent and feasible tax planning strategies. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained based on the technical merits of the position.

The Company adopted ASU No. 2016-16, "Intra-Entity Transfers of Assets Other Than Inventory," on January 1, 2018. Information regarding our adoption of this new accounting standard and its impact on the Company's consolidated financial statements is provided below under the heading "Adoption of new accounting standards."

Cash and cash equivalents. Includes cash and all highly liquid investments with original maturities of three months or less, which are considered cash equivalents. The carrying value of cash equivalents approximates fair value due to their short-term maturity. Investments with maturities of more than three months are classified as marketable securities. Interest earned is classified in Interest income in the Consolidated Statements of Operations.

On January 1, 2018, the Company adopted ASU No. 2016-18, "Restricted Cash" ("ASU No. 2016-18"). ASU No. 2016-18 requires that amounts generally described as restricted cash and restricted cash equivalents be presented with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts presented on an entity's statement of cash flows. A table presenting the beginning-of-period and end-of-period cash amounts from the Company's Consolidated Balance Sheets and the total cash amounts presented in the accompanying Consolidated Cash Flow Statements is provided below under the heading "Adoption of new accounting standards."

Property, equipment and leasehold improvements. The Company leases all of its facilities and certain equipment. These leases are all classified as operating leases in accordance with FASB ASC Topic 840, Leases. The cost of these operating leases, including any contractual rent increases, rent concessions and landlord incentives, is recognized ratably over the life of the related lease agreement. Lease expense was $93.5 million, $87.9 million and $38.0 million in 2018, 2017 and 2016, respectively.

Equipment, leasehold improvements and other fixed assets owned by the Company are recorded at cost less accumulated depreciation. Except for leasehold improvements, these fixed assets are depreciated using the straight-line method over the estimated useful life of the underlying asset. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life of the improvement or the remaining term of the related lease. The Company's total depreciation expense was $68.6 million, $63.9 million and $37.2 million in 2018, 2017 and 2016, respectively. The Company's total fixed assets, less accumulated depreciation and amortization, consisted of the following (in thousands):



	Useful Life	December 31,
Category	(Years)	2018			2017
Computer equipment and software	2-7	$	210,955		$	189,015
Furniture and equipment	3-8	85,002			67,288
Leasehold improvements	2-15	218,405			175,716
		514,362			432,019
Less — accumulated depreciation and amortization		(246,697		)	(210,512		)
Property, equipment and leasehold improvements, net		$	267,665		$	221,507

The Company incurs costs to develop internal-use software used in its operations, and certain of those costs meeting the criteria outlined in FASB ASC Topic 350, "Intangibles - Goodwill and Other," are capitalized and amortized over future periods. Net capitalized development costs for internal-use software were $37.4 million and $26.9 million at December 31, 2018 and 2017, respectively, which is included in the Computer equipment and software category above. Amortization expense for capitalized internal-use software development costs, which is classified in Depreciation in the Consolidated Statements of Operations, totaled $13.2 million, $9.9 million and $8.8 million in 2018, 2017 and 2016, respectively.

Finite-lived intangible assets. The Company has finite-lived intangible assets that are amortized against earnings using the straight-line method over the expected useful life of the underlying asset. Changes in intangible assets subject to amortization during the two-year period ended December 31, 2018 were as follows (in thousands):



December 31, 2018	Customer Relationships			Software			Content			Other			Total
Gross cost at December 31, 2017 (1)	$	1,200,316		$	123,424		$	104,313		$	54,929		$	1,482,982
Divestitures (2)	(45,175		)	(321		)	(473		)	(160		)	(46,129		)
Write-off of fully amortized intangible assets	(303		)	(11,715		)	(669		)	(3,311		)	(15,998		)
Foreign currency translation impact and other (3)	(23,182		)	(687		)	(4,329		)	204			(27,994		)
Gross cost	1,131,656			110,701			98,842			51,662			1,392,861
Accumulated amortization (4)	(184,918		)	(38,901		)	(92,717		)	(33,760		)	(350,296		)
Balance at December 31, 2018	$	946,738		$	71,800		$	6,125		$	17,902		$	1,042,565



December 31, 2017	Customer Relationships			Software			Content			Other			Total
Gross cost at December 31, 2016	$	63,369		$	16,025		$	3,728		$	33,645		$	116,767
Additions due to acquisitions (5)	1,253,312			180,787			141,707			24,384			1,600,190
Write-off of fully amortized intangible assets	—			—			(4,227		)	—			(4,227		)
Reclassified as held-for-sale (6)	(140,156		)	(69,012		)	(38,593		)	(2,711		)	(250,472		)
Foreign currency translation impact	23,791			(4,376		)	1,698			(389		)	20,724
Gross cost (1)	1,200,316			123,424			104,313			54,929			1,482,982
Accumulated amortization (4)	(92,983		)	(26,344		)	(47,475		)	(24,158		)	(190,960		)
Balance at December 31, 2017 (1)	$	1,107,333		$	97,080		$	56,838		$	30,771		$	1,292,022


(1)	Excludes certain amounts related to held-for-sale operations.


(2)	Represents amounts related to divested businesses. See Note 2 — Acquisitions and Divestitures for additional information.


(3)	Includes the foreign currency translation impact and certain other adjustments.


(4)	Finite-lived intangible assets are amortized using the straight-line method over the following periods: Customer relationships—4 to 13 years; Software—3 to 7 years; Content—1.5 to 5 years; and Other —2 to 5 years.


(5)	The additions were primarily due to the Company's acquisitions of CEB Inc. and L2, Inc. during April 2017 and March 2017, respectively. See Note 2 — Acquisitions and Divestitures for additional information.


(6)	Represents amounts reclassified (net) as held-for-sale assets related to the CEB Talent Assessment business. See Note 2 — Acquisitions and Divestitures for additional information.

Amortization expense related to finite-lived intangible assets was $187.0 million, $176.3 million and $24.8 million in 2018, 2017 and 2016, respectively. The estimated future amortization expense by year for finite-lived intangible assets is as follows (in thousands):



2019	$	129,394
2020	122,756
2021	102,338
2022	92,801
2023 and thereafter	595,276
	$	1,042,565

Goodwill. Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair values of the tangible and identifiable intangible net assets acquired. Evaluations of the recoverability of goodwill are performed in accordance with FASB ASC Topic 350, which requires an annual assessment of potential goodwill impairment at the reporting unit level and whenever events or changes in circumstances indicate that the carrying value of goodwill may not be recoverable. The annual assessment of the recoverability of recorded goodwill can be based on either a qualitative or quantitative assessment or a combination of the two approaches. Both methods utilize estimates which, in turn, require judgments and assumptions regarding future trends and events. As a result, both the precision and reliability of the resulting estimates are subject to uncertainty. If our annual goodwill impairment evaluation determines that the fair value of a reporting unit is less than its related carrying amount, we may recognize an impairment charge. In connection with our most recent annual impairment test of goodwill during the quarter ended September 30, 2018, which indicated no impairment of recorded goodwill, the Company utilized the quantitative approach in assessing the fair values of its reporting units relative to their respective carrying values.

The following table presents changes to the carrying amount of goodwill by segment, including the Company's Other segment, during the two-year period ended December 31, 2018 (in thousands):



	Research			Conferences			Consulting			Other			Total
Balance at December 31, 2016 (1)	$	595,450		$	46,523		$	96,480		$	—		$	738,453
Additions due to acquisitions (2)	2,042,514			140,914			—			274,363			2,457,791
Reclassified as held-for-sale (3)	—			—			—			(212,994		)	(212,994		)
Foreign currency translation impact	(18,287		)	483			1,318			20,530			4,044
Balance at December 31, 2017	2,619,677			187,920			97,798			81,899			2,987,294
Divestitures (4)	(2,500		)	—			—			(90,078		)	(92,578		)
Foreign currency translation impact and other (5)	21,241			(266		)	(734		)	8,179			28,420
Balance at December 31, 2018	$	2,638,418		$	187,654		$	97,064		$	—		$	2,923,136


(1)	The Company does not have any accumulated goodwill impairment losses.


(2)	The 2017 goodwill additions are due to the acquisitions of CEB Inc. and L2, Inc. during April 2017 and March 2017, respectively. See Note 2 – Acquisitions and Divestitures for additional information.


(3)	Represents amounts reclassified as held-for-sale assets related to the CEB Talent Assessment business. See Note 2 – Acquisitions and Divestitures for additional information.


(4)	Represents amounts related to divested businesses. See Note 2 – Acquisitions and Divestitures for additional information.


(5)	Includes the foreign currency translation impact and certain measurement period adjustments related to the acquisition of CEB Inc.

Impairment of long-lived assets. The Company's long-lived assets primarily consist of intangible assets other than goodwill and property, equipment and leasehold improvements. The Company reviews its long-lived asset groups for impairment whenever events or changes in circumstances indicate that the carrying amount of the respective asset may not be recoverable. Such evaluation may be based on a number of factors, including current and projected operating results and cash flows, and changes in management’s strategic direction as well as external economic and market factors. The Company evaluates the recoverability of these assets by determining whether their carrying values can be recovered through undiscounted future operating cash flows. If events or circumstances indicate that the carrying values might not be recoverable based on undiscounted future operating cash flows, an impairment loss would be recognized. The amount of impairment, if any, is measured based on the difference between the projected discounted future operating cash flows, using a discount rate reflecting the Company’s average cost of funds, and the carrying value of the asset. The Company did not record any impairment charges for long-lived asset groups during the three-year period ended December 31, 2018.

Pension obligations. The Company has defined benefit pension plans in several of its international locations (see Note 13 — Employee Benefits). Benefits earned under these plans are generally based on years of service and level of employee compensation. The Company accounts for its defined benefit plans in accordance with the requirements of FASB ASC Topic 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations. The Company recognized $3.9 million, $3.6 million and $3.5 million of pension expense in 2018, 2017 and 2016, respectively.

Debt. The Company presents amounts borrowed in the Consolidated Balance Sheets at amortized cost, net of deferred financing fees. Interest accrued on amounts borrowed is classified as Interest expense in the Consolidated Statements of Operations. The Company had $2.3 billion of principal amount of debt outstanding at December 31, 2018 compared to $3.3 billion at December 31, 2017, which reflects the Company's significant principal repayments on its debt subsequent to the completion of the CEB Inc. acquisition. Note 5 — Debt provides information regarding the Company's debt.

Foreign currency exposure. The functional currency of our foreign subsidiaries is typically the local currency. All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense items are translated at average exchange rates for the year. The resulting translation adjustments are recorded as foreign currency translation adjustments, a component of Accumulated other comprehensive (loss) income, net within the Stockholders’ Equity section of the Consolidated Balance Sheets.

Currency transaction gains or losses arising from transactions denominated in currencies other than the functional currency of a subsidiary are recognized in results of operations in Other income, net within the Consolidated Statements of Operations. The Company had net currency transaction gains (losses) of $9.2 million, $(5.5) million and $(0.4) million in 2018, 2017 and 2016, respectively. The Company enters into foreign currency forward exchange contracts to mitigate the effects of adverse fluctuations in foreign currency exchange rates on certain transactions. Those contracts generally have short durations and are recorded at fair value with both realized and unrealized gains and losses recorded in Other income, net. The net gain (loss) from foreign currency forward exchange contracts was $(10.4) million, $0.8 million and $(0.3) million in 2018, 2017 and 2016, respectively.

Comprehensive income. The Company reports comprehensive income in a separate statement called the Consolidated Statements of Comprehensive Income, which is included herein. The Company's comprehensive income disclosures are included in Note 7 — Stockholders' Equity.

Fair value disclosures. The Company has a limited number of assets and liabilities that are adjusted to fair value at each balance sheet date. The Company’s fair value disclosures are included in Note 12 — Fair Value Disclosures.

Concentrations of credit risk. Assets that may subject the Company to concentration of credit risk consist primarily of short-term, highly liquid investments classified as cash equivalents, fees receivable, contract assets, interest rate swaps and a pension reinsurance asset. The majority of the Company’s cash equivalent investments and its interest rate swap contracts are with investment grade commercial banks. Fees receivable and contract asset balances deemed to be collectible from customers have limited concentration of credit risk due to our diverse customer base and geographic dispersion. The Company’s pension reinsurance asset (see Note 13 — Employee Benefits) is maintained with a large international insurance company that was rated investment grade as of December 31, 2018 and 2017.

Stock repurchase programs. The Company records the cost to repurchase its own common shares as treasury stock. During 2018, 2017 and 2016, the Company used $260.8 million, $41.3 million and $59.0 million, respectively, in cash for stock repurchases (see Note 7 — Stockholders’ Equity for additional information). Shares repurchased by the Company are added to treasury shares and are not retired.

Adoption of new accounting standards. The Company adopted the accounting standards described below during 2018:

Certain Tax Effects Stranded In Accumulated Other Comprehensive Income — On April 1, 2018, the Company early adopted ASU No. 2018-02, "Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" ("ASU No. 2018-02"). ASU No. 2018-02 provides an entity with the option to reclassify to retained earnings the tax effects from items that have been stranded in accumulated other comprehensive income as a result of the U.S. Tax Cuts and Jobs Act of 2017 (the “Act”). Entities can adopt ASU No. 2018-02 using one of two transition methods: (i) retrospective to each period wherein the income tax effects of the Act related to items remaining in accumulated other comprehensive income are recognized or (ii) at the beginning of the period of adoption. Gartner elected to early adopt ASU No. 2018-02 as of the beginning of the second quarter of 2018, which resulted in a reclassification of $0.6 million of stranded tax amounts related to the Act from Accumulated other comprehensive (loss) income, net to Accumulated earnings. ASU No. 2018-02 had no impact on the Company's operating results in 2018.

Stock Compensation Award Modifications — On January 1, 2018, the Company adopted ASU No. 2017-09, "Compensation—Stock Compensation - Scope of Modification Accounting" ("ASU No. 2017-09"). ASU No. 2017-09 provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The adoption of ASU No. 2017-09 had no impact on the Company's consolidated financial statements.

Retirement Benefits Cost Presentation — On January 1, 2018, the Company adopted ASU No. 2017-07, "Compensation—Retirement Benefits" ("ASU No. 2017-07"). ASU No. 2017-07 improves the reporting of net benefit cost in the financial statements, provides additional guidance on the presentation of net benefit cost in the income statement and clarifies the components eligible for capitalization. The adoption of ASU No. 2017-07 had an immaterial impact on the classification of benefit expense on the Company's Consolidated Statements of Operations.

Partial Sales of Non-financial Assets — On January 1, 2018, the Company adopted ASU No. 2017-05, "Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Non-financial Assets" ("ASU No. 2017-05"). ASU No. 2017-05 clarifies the scope of the FASB’s guidance on non-financial asset derecognition as well as the accounting for partial sales of non-financial assets. It conforms the derecognition guidance on non-financial assets with the model for revenue transactions. The adoption of ASU No. 2017-05 had no impact on the Company's consolidated financial statements.

Definition of a Business — On January 1, 2018, the Company adopted ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU No. 2017-01"). ASU No. 2017-01 changes the U.S. GAAP definition of a business. Such change can impact the accounting for asset purchases, acquisitions, goodwill impairment and other assessments. The adoption of ASU No. 2017-01 had no impact on the Company's consolidated financial statements.

Presentation of Restricted Cash — On January 1, 2018, the Company adopted ASU No. 2016-18, "Restricted Cash" ("ASU No. 2016-18"). ASU No. 2016-18 requires that amounts generally described as restricted cash and restricted cash equivalents be presented with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts presented on an entity's statement of cash flows. ASU No. 2016-18 must be applied using a retrospective transition method to each comparative period presented in an entity's financial statements.

As a result of the adoption of ASU No. 2016-18, the Company's restricted cash balances are now included in the beginning-of-period and end-of-period total amounts presented on the accompanying Consolidated Statements of Cash Flows. When compared to the Company's previously issued statement of cash flows for 2017, the adoption of ASU No. 2016-18 resulted in: (i) an increase of $7.0 million in cash used in investing activities; (ii) an increase of $18.2 million in the end-of-period total cash amount; and (iii) an increase of $25.1 million in the beginning-of-period total cash amount. The corresponding effects on the statement of cash flows for 2016 were: (i) an increase of $14.0 million in cash used in investing activities; (ii) an increase of $25.1 million in the end-of-period total cash amount; and (iii) an increase of $39.1 million in the beginning-of-period total cash amount.

Below is a table presenting the beginning-of-period and end-of-period cash amounts from the Company's Consolidated Balance Sheets and the total cash amounts presented in the accompanying Consolidated Cash Flow Statements (in thousands).



	December 31,
	2018		2017		2016		2015
Cash and cash equivalents	$	156,368	$	538,908	$	474,233	$	372,976
Restricted cash classified in (1), (2):
Prepaid expenses and other current assets	2,295		15,148		25,121		13,505
Other assets	—		3,002		—		25,626
Cash classified as held-for-sale (3)	—		10,000		—		—
Cash and cash equivalents and restricted cash per the Consolidated Statements of Cash Flows	$	158,663	$	567,058	$	499,354	$	412,107

(1)

Restricted cash consists of escrow accounts established in connection with certain of the Company's business acquisitions. Generally, such cash is restricted to use due to provisions contained in the underlying asset purchase agreement. The Company will disburse the restricted cash to the sellers of the businesses upon satisfaction of any contingencies described in such agreements (e.g., potential indemnification claims, etc.).


(2)	Restricted cash is recorded in Prepaid expenses and other current assets and Other assets in the Company's consolidated balance sheets with the short-term or long-term classification dependent on the projected timing of disbursements to the sellers.


(3)	Represents cash classified as a held-for-sale asset for the CEB Talent Assessment business that was acquired as part of the CEB Inc. acquisition. See Note 2 — Acquisitions and Divestitures for additional information.

Income Taxes — On January 1, 2018, the Company adopted ASU No. 2016-16, "Intra-Entity Transfers of Assets Other Than Inventory" ("ASU No. 2016-16"). ASU No. 2016-16 accelerates the recognition of taxes on certain intra-entity transactions. U.S. GAAP previously required deferral of the income tax implications of an intercompany sale of assets until the assets were sold to a third party or recovered through use. Under ASU No. 2016-16, the seller’s tax effects and the buyer’s deferred taxes on asset transfers are immediately recognized upon the sale.

Pursuant to the transition rules in ASU No. 2016-16, any taxes attributable to pre-2018 intra-entity transfers that were previously deferred should be accelerated and recorded to accumulated earnings on the date of adoption. As a result of this transition rule, certain of the Company's balance sheet income tax accounts pertaining to pre-2018 intra-entity transfers, which aggregated $13.7 million, were reversed against accumulated earnings on January 1, 2018. Pursuant to the provisions of ASU No. 2016-16, the Company recorded an income tax benefit of $6.8 million in 2018 related to intra-entity transfers upon the merger of certain foreign subsidiaries. ASU No. 2016-16 could have a material impact on the Company's consolidated financial statements in the future, depending on the nature, size and tax consequences of intra-entity transfers, if any.

Statement of Cash Flows — On January 1, 2018, the Company adopted ASU No. 2016-15, "Classification of Certain Cash Receipts and Cash Payments" ("ASU No. 2016-15"). ASU No. 2016-15 sets forth classification requirements for certain cash flow transactions. The adoption of ASU No. 2016-15 had no impact on the Company's consolidated financial statements.

Financial Instruments Recognition and Measurement — On January 1, 2018, the Company adopted ASU No. 2016-01, "Financial Instruments Overall - Recognition and Measurement of Financial Assets and Liabilities" ("ASU No. 2016-01"), to address certain aspects of recognition, measurement, presentation and disclosure of financial instruments. Among the significant changes required by ASU No. 2016-01 is that equity investments are to be measured at fair value with changes in fair value recognized in net income. The adoption of ASU No. 2016-01 had no impact on the Company's consolidated financial statements.

Revenue Recognition — On January 1, 2018, the Company adopted ASU No. 2014-09, "Revenue from Contracts with Customers," as amended ("ASU No. 2014-09"). The adoption of the standard did not have a material impact on the Company's consolidated financial statements. However, as required by ASU No. 2014-09, the Company's disclosures around revenue recognition have been significantly expanded. Additionally, the Company's accounting policies have been updated to reflect the adoption of ASU No. 2014-09.

The following sections provide an overview of the Company's revenues by segment along with the required disclosures under the new revenue recognition standard.

Our business and our revenues

Gartner currently delivers its products and services globally through three business segments: Research, Conferences and Consulting. Our revenues from those business segments are discussed below.

Research

Research provides trusted, objective insights and advice on the mission-critical priorities of leaders across all functional areas of an enterprise through research and other reports, briefings, proprietary tools, access to our analysts and advisors, peer networking services and membership programs that enable our clients to make better decisions. Gartner's traditional strengths in information technology (“IT”), marketing and supply chain research were enhanced in 2017 with Gartner's acquisition of CEB Inc., which added CEB's best practice and talent management research insights across a range of business functions, to include human resources, finance, sales and legal.

Research revenues are mainly derived from subscription contracts for research products, representing approximately 90% of the segment’s revenue. The related revenues are deferred and recognized ratably over the applicable contract term (i.e., as we provide services over the contract period). Fees derived from assisting organizations in selecting the right business software for their needs are recognized at a point in time (i.e., when the lead is provided to the vendor).

The Company enters into subscription contracts for research products that generally are for twelve-month periods or longer. Approximately 75% to 80% of our annual and multi-year Research subscription contracts provide for billing of the first full service period upon signing. In subsequent years, multi-year subscription contracts are normally billed prior to the contract’s anniversary date. Our other Research subscription contracts are usually invoiced in advance, commencing with the contract signing, on (i) a quarterly, monthly or other recurring basis or (ii) in accordance with a customized invoicing schedule. Research contracts are generally non-cancelable and non-refundable, except for government contracts that may have cancellation or fiscal funding clauses, which historically have not produced material cancellations. It is our policy to record the amount of a subscription contract that is billable as a fee receivable at the time the contract is signed with a corresponding amount as deferred revenue because the contract represents a legally enforceable claim.

Conferences

Conferences (formerly called Events) provides business professionals across the organization the opportunity to learn, share and network. From our flagship CIO conference Gartner IT Symposium, to industry-leading conferences focused on specific business roles and topics, to member-driven sessions, our offerings enable attendees to experience the best of Gartner insight and advice live.

We earn revenues from both the attendees and exhibitors at our conferences and meetings. Attendees are generally invoiced for the full attendance fee upon their completion of an online registration form or their signing of a contract, while exhibitors typically make several individual payments commencing with the signing of a contract. We collect almost all of the invoiced amounts in advance of the related activity, resulting in the recording of deferred revenue. We recognize both the attendee and exhibitor revenue as we satisfy our related performance obligations (i.e., when the related activity is held).

The Company defers certain costs directly related to specific conferences and meetings and expenses those costs in the period during which the related activity occurs. The Company's policy is to defer only those costs that are incremental and directly attributable to a specific activity, primarily prepaid site and production services costs. Other costs of organizing and producing our activities, primarily Company personnel and non-conference specific expenses, are expensed in the period incurred. At the end of each fiscal quarter, the Company assesses whether the expected direct costs of producing a scheduled activity will exceed the projected revenues. If such costs are expected to exceed revenues, the Company records the expected loss in the period determined.

Consulting

Consulting provides customized solutions to unique client needs through on-site, day-to-day support, as well as proprietary tools for measuring and improving IT performance with a focus on cost, performance, efficiency and quality, and contract optimization services.

Consulting revenues, primarily derived from custom consulting and measurement services, are principally generated from fixed fee or time and materials engagements. Revenues from fixed fee engagements are recognized as we work to satisfy our performance obligations, while revenues from time and materials engagements are recognized as work is delivered and/or services are provided. In both of these circumstances, we satisfy our performance obligations and control of the services are passed to our customers over time (i.e., during the duration of the contract or consulting engagement). On a contract-by-contract basis, we typically use actual labor hours incurred compared to total expected labor hours to measure the Company’s performance in respect of our fixed fee engagements. If our labor and other costs on an individual contract are expected to exceed the total contract value or the contract’s funded ceiling amount, the Company reflects an adjustment to the contract’s overall profitability in the period determined. Revenues related to contract optimization engagements are contingent in nature and are only recognized at the point in time when all of the conditions related to their payment have been satisfied.

Consulting customers are invoiced based on the specific terms and conditions in their underlying contracts. We typically invoice our Consulting customers after we have satisfied some or all of the related performance obligations and the related revenue has been recognized. We record fees receivable for amounts that are billed or billable. We also record contract assets, which represent amounts for which we have recognized revenue but lack the unconditional right to payment as of the balance sheet date due to our required continued performance under the relevant contract, progress billing milestones or other billing-related restrictions. The Company’s contract assets are discussed below.

Overview of ASU No. 2014-09

ASU No. 2014-09 requires a five-step evaluative process that consists of:


(1)	Identifying the contract with the customer;


(2)	Identifying the performance obligations in the contract;


(3)	Determining the transaction price for the contract;


(4)	Allocating the transaction price to the performance obligations in the contract; and


(5)	Recognizing revenue when (or as) performance obligations are satisfied.

ASU No. 2014-09 is intended to clarify the principles for recognizing revenue by removing inconsistencies and weaknesses in previously existing revenue recognition rules; provide a more robust framework for addressing revenue recognition issues; improve comparability of revenue recognition practices across entities, industries, jurisdictions and capital markets; and provide more useful information to users of financial statements through improved disclosures.

The Company adopted ASU No. 2014-09 using the modified retrospective method of adoption. Under this method of adoption, the cumulative effect of applying the new standard is recorded at the date of initial application, with no restatement of the comparative prior periods presented. The adoption of ASU No. 2014-09 did not result in a cumulative effect adjustment to the Company's Accumulated earnings in its consolidated financial statements. However, the adoption of the new standard required reclassifications of certain amounts presented in the Company’s consolidated balance sheet. As of January 1, 2018, these items were (i) the reclassification of certain fees receivable that met the definition of a contract asset, aggregating $26.7 million, from Fees receivable, net to Prepaid expenses and other current assets; and (ii) the reclassification of a refund liability, aggregating $6.2 million, from the allowance for fees receivable to Accounts payable and accrued liabilities.

Related to our adoption of ASU No. 2014-09, we elected to (i) apply the provisions of this new accounting guidance only to contracts that were not completed at the date of initial application and (ii) utilize a practical expedient whereby we reflected the aggregate effect of all contract modifications that occurred prior to January 1, 2018 (rather than retrospectively restating the affected contracts) when identifying our satisfied and unsatisfied performance obligations, determining the transaction prices with our customers, and allocating such transaction prices to our satisfied and unsatisfied performance obligations. These two elections had no financial impact.

Prior to January 1, 2018, the Company recognized revenue in accordance with then-existing U.S. GAAP and SEC Staff Accounting Bulletin No. 104, "Revenue Recognition" (“prior GAAP”). Under both ASU No. 2014-09 and prior GAAP, revenue can only be recognized when all of the required criteria are met. Although there were certain changes to the Company’s revenue recognition policies and procedures effective January 1, 2018 with the adoption of ASU No. 2014-09, there were no material differences between the pattern and timing of revenue recognition under ASU No. 2014-09 and prior GAAP. The accompanying Consolidated Statements of Operations present revenues net of any sales or value-added taxes that we collect from customers and remit to government authorities.

ASU No. 2014-09 requires that we assess at inception all of the promises in a customer contract to determine if a promise is a separate performance obligation. To identify our performance obligations, we consider all of the services promised in a customer contract, regardless of whether they are explicitly stated or implied by customary business practices. If we conclude that a service is separately identifiable and distinct from the other offerings in a contract, we account for such a promise as a separate performance obligation.

If a customer contract has more than one performance obligation, then the total contract consideration is allocated among the separate deliverables based on their stand-alone selling prices, which are determined based on the prices at which the Company discretely sells the stand-alone services. If a contract includes a discount or other pricing concession, the transaction price is allocated among the performance obligations on a proportionate basis using the relative stand-alone selling prices of the individual deliverables being transferred to the customer, unless the discount or other pricing concession can be ascribed to specifically identifiable performance obligations.

The contracts with our customers delineate the final terms and conditions of the underlying arrangements, including product descriptions, subscription periods, deliverables, quantities and the price of each service purchased. Since the transaction price of almost all of our customer contracts is typically agreed upon upfront and generally does not fluctuate during the duration of the contract, variable consideration is insignificant. The Company may engage in certain financing transactions with customers but these arrangements have been limited in number and not material.

Required Disclosures under ASU No. 2014-09

ASU No. 2014-09 requires significantly expanded disclosures around the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. These additional disclosures are provided below.

Disaggregated Revenues

We believe that disaggregating the Company’s revenues by primary geographic location and the timing of when revenue is recognized achieves the disclosure objectives in ASU No. 2014-09. Our disaggregated revenue information by reportable segment, including our Other segment, is presented for the years indicated in the tables below (in thousands).

Year Ended December 31, 2018



	Research		Conferences		Consulting		Other (1)		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,994,016	$	256,219	$	205,874	$	58,843	$	2,514,952
Europe, Middle East and Africa	737,129		105,909		119,258		38,194		1,000,490
Other International	374,619		48,333		28,535		8,525		460,012
Total revenues	$	3,105,764	$	410,461	$	353,667	$	105,562	$	3,975,454

Year Ended December 31, 2017



	Research		Conferences		Consulting		Other (1)		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,600,847	$	210,698	$	188,022	$	92,799	$	2,092,366
Europe, Middle East and Africa	597,943		86,567		111,792		59,119		855,421
Other International	272,490		40,638		27,847		22,732		363,707
Total revenues	$	2,471,280	$	337,903	$	327,661	$	174,650	$	3,311,494

Year Ended December 31, 2016



	Research		Conferences		Consulting		Other		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,178,575	$	162,162	$	179,011	$	—	$	1,519,748
Europe, Middle East and Africa	434,753		72,926		109,042		—		616,721
Other International	243,673		33,517		30,881		—		308,071
Total revenues	$	1,857,001	$	268,605	$	318,934	$	—	$	2,444,540


(1)	The decline in Other segment revenues in 2018 compared to 2017 was due to divestitures. Information regarding the divestitures is included in Note 2 – Acquisitions and Divestitures.


(2)	Revenues are reported based on where the sale is fulfilled.

The Company’s revenues are generated primarily through direct sales to clients by domestic and international sales forces and a network of independent international sales agents. Most of the Company’s products and services are provided on an integrated worldwide basis and, because of this integrated delivery approach, it is not practical to precisely separate our revenues by geographic location. Accordingly, revenue information presented in the above tables is based on internal allocations, which involve certain management estimates and judgments.

Year Ended December 31, 2018



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	2,851,176	$	—	$	294,397	$	86,667	$	3,232,240
Transferred at a point in time (2)	254,588		410,461		59,270		18,895		743,214
Total revenues	$	3,105,764	$	410,461	$	353,667	$	105,562	$	3,975,454

Year Ended December 31, 2017



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	2,275,377	$	—	$	269,720	$	141,331	$	2,686,428
Transferred at a point in time (2)	195,903		337,903		57,941		33,319		625,066
Total revenues	$	2,471,280	$	337,903	$	327,661	$	174,650	$	3,311,494

Year Ended December 31, 2016



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	1,710,786	$	—	$	267,809	$	—	$	1,978,595
Transferred at a point in time (2)	146,215		268,605		51,125		—		465,945
Total revenues	$	1,857,001	$	268,605	$	318,934	$	—	$	2,444,540

(1)

These Research revenues were recognized in connection with performance obligations that were satisfied over time using a time-elapsed output method to measure progress. The corresponding Consulting revenues were recognized over time using labor hours as an input measurement basis. Other revenues in this category were recognized using either a time-elapsed output method, performance-based milestone approach or labor hours, depending on the nature of the underlying customer contract.


(2)	The revenues in this category were recognized in connection with performance obligations that were satisfied at the point in time the contractual deliverables were provided to the customer.

Determining a measure of progress for performance obligations that are satisfied over time and when control transfers for performance obligations that are satisfied at a point in time requires us to make judgments that affect the timing of when revenue is recognized. A key factor in this determination is when the customer is able to direct the use of, and can obtain substantially all of the benefits from, the deliverable.

For performance obligations recognized in accordance with a time-elapsed output method, the Company’s efforts are expended consistently throughout the contractual period and the Company transfers control evenly by providing stand-ready services. For performance obligations satisfied under our Consulting fixed fee and time and materials engagements, we believe that labor hours are the best measure of depicting the Company’s progress because labor output corresponds directly to the value of the Company’s performance to date as control is transferred. In our Other segment, we selected a method to assess the completion of our performance obligations that best aligned with the specific characteristics of the individual customer contract. We believe that these methods to measure progress provide a reasonable and supportable determination as to when we transfer services to our customers.

For customer contracts that are greater than one year in duration, the aggregate amount of the transaction price allocated to performance obligations that are unsatisfied (or partially unsatisfied) as of December 31, 2018 was approximately $2.7 billion. The Company expects to recognize $1,620.4 million, $874.5 million and $186.5 million of this revenue (most of which pertains to Research) during the year ending December 31, 2019, the year ending December 31, 2020 and thereafter, respectively. The Company applies a practical expedient allowed in ASU No. 2014-09 and, accordingly, it does not disclose such performance obligation information for customer contracts that have original durations of one year or less. Our performance obligations for contracts meeting this ASU No. 2014-09 disclosure exclusion primarily include: (i) stand-ready services under Research subscription contracts; (ii) holding conferences where attendees and exhibitors can participate; and (iii) providing customized Consulting solutions for clients under fixed fee and time and materials engagements. The remaining duration of these performance obligations is generally less than one year, which aligns with the period that the parties have enforceable rights and obligations under the affected contracts.

Customer Contract Assets and Liabilities

The timing of the recognition of revenues, and the amount and timing of our billings and cash collections, as well as upfront customer payments, result in the recording of both assets and liabilities on our Consolidated Balance Sheets.

The payment terms and conditions in our customer contracts vary. In some cases, customers prepay and, in other cases, after we conduct a credit evaluation, payment may be due in arrears. Because the timing of the delivery of our services typically differs from the timing of customer payments, the Company recognizes either a contract asset (we perform either fully or partially under the contract but a contingency remains) or a contract liability (upfront customer payments precede our performance, resulting in deferred revenue). Amounts recorded as contract assets are reclassified to fees receivable when all of the outstanding conditions have been resolved and our right to payment becomes unconditional. Contracts with payments due in arrears are also recognized as fees receivable. As our contractual performance obligations are satisfied over time or at a point in time, the Company correspondingly relieves its contract liabilities and records the associated revenue.

The table below provides information regarding certain of the Company’s balance sheet accounts that pertain to its contracts with customers, excluding held-for-sale businesses (in thousands):



	December 31,
	2018		2017
Assets:
Fees receivable, gross (1)	$	1,262,818	$	1,162,871

Contract assets (2)	$	26,119	$	26,672

Contract liabilities:
Deferred revenues (current liability) (3)	$	1,745,244	$	1,630,198
Non-current deferred revenues (3)	21,194		16,205
Total contract liabilities	$	1,766,438	$	1,646,403


(1)	Fees receivable represent the unconditional right of payment from our customers and include both billed and unbilled amounts.

(2)

Contract assets represent recognized revenue for which we do not have an unconditional right to payment as of the balance sheet date because the project may be subject to a progress billing milestone or some other billing restriction. In the accompanying Consolidated Balance Sheets, contract assets are recorded in Prepaid expenses and other current assets as of December 31, 2018 and Fees receivable, net as of December 31, 2017.


(3)	Deferred revenues represent amounts (i) for which the Company has received an upfront customer payment or (ii) that pertain to recognized fees receivable. Both situations occur before the completion of our performance obligation(s).

During 2018, the Company recognized $1,287.8 million of revenue that was attributable to deferred revenues that were recorded at December 31, 2017. That amount primarily consisted of (i) Research and Other revenues that were recognized ratably as control of the goods or services passed to the customer and (ii) Conferences revenue pertaining to conferences that occurred during the reporting period. In 2018, the Company recorded no material impairments related to its contract assets. In the normal course of business, the Company does not recognize revenues from performance obligations satisfied in prior periods.

Allowance for Losses and the Revenue Reserve

As of December 31, 2017, the Company maintained an allowance for losses that included a bad debt allowance and a revenue reserve. Provisions to the Company’s allowance for losses were charged against earnings as either a reduction in revenues or an increase in expense. Effective with the adoption of ASU No. 2014-09 on January 1, 2018, the allowance for losses, which is classified as an offset to the gross amount of fees receivable, and the related charge against earnings (i.e., bad debt expense) is now comprised solely of estimated uncollectible fees receivable due to credit and other associated risks. The revenue reserve previously reported as part of the allowance for losses has been reclassified and is now reported as a liability in accordance with ASU No. 2014-09.

The revenue reserve is maintained for amounts deemed to be uncollectible for reasons other than bad debt. When determining the amount of the revenue reserve, the Company uses an expected-value method that is based on current estimates and a portfolio of data from its historical experience. Due to the common characteristics and similar attributes of our customers and contracts, which provide relevant and predictive evidence about our projected future liability, an expected-value method is reasonable and appropriate. However, the determination of the revenue reserve is inherently judgmental and requires the use of certain estimates. Changes in estimates are recorded in the period that they are identified. As of December 31, 2018, the revenue reserve balance was $7.4 million and adjustments to the account in 2018 were not significant.

The allowance for losses for bad debts is based on historical loss experience, an assessment of current economic conditions, the aging of outstanding receivables, the financial health of specific clients and probable losses. This evaluation is inherently judgmental and requires the use of estimates. The allowance for losses for bad debts is periodically re-evaluated and adjusted as more information about the ultimate collectability of fees receivable becomes available. Circumstances that could cause such allowance for losses to increase include changes in our clients’ liquidity and credit quality, other factors negatively impacting our clients’ ability to pay their obligations as they come due, and the effectiveness of our collection efforts.

Costs of obtaining and fulfilling a customer contract

Upon the signing of a customer contract, the Company capitalizes the related commission as a recoverable direct incremental cost of obtaining the underlying contract and records a corresponding commission payable. No other amounts are capitalized as a cost of obtaining or fulfilling a customer contract because no expenditures have been identified that meet the requisite capitalization criteria. For Research, Consulting and Other, we generally use the straight-line method of amortization for deferred commissions over a period that is based on the projected recoverability for such costs, using factors such as the underlying contract period, the timing of when the corresponding revenues will be earned and the anticipated term of the engagement. For Conferences, deferred commissions are expensed during the period when the related conference occurs.

Under all circumstances, deferred commissions are amortized over a period that does not exceed one year. During 2018, 2017 and 2016, such amortization expense was $304.8 million, $230.5 million and $180.2 million, respectively, and was included in SG&A expense in the accompanying Consolidated Statements of Operations. The Company recorded no material impairments of its deferred commissions during the three-year period ended December 31, 2018.

Accounting standards issued but not yet adopted. The FASB has issued accounting standards that had not yet become effective as of December 31, 2018 and may impact the Company’s consolidated financial statements or related disclosures in future periods. Those standards and their potential impact are discussed below.

Accounting standards effective in 2019

Targeted Improvements to Accounting for Hedging Activities — In August 2017, the FASB issued ASU No. 2017-12, "Derivatives and Hedging" ("ASU No. 2017-12"). ASU No. 2017-12 is intended to improve the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. In addition to that main objective, the standard makes certain targeted improvements to simplify the application of hedge accounting guidance in current U.S. GAAP. On January 1, 2019, the Company adopted ASU No. 2017-12. The adoption of ASU No. 2017-12 had no impact on the Company's consolidated financial statements.

Leases — In February 2016, the FASB issued ASU No. 2016-02, "Leases," as amended ("ASU No. 2016-02"), which substantively modifies the accounting and disclosure requirements for lease arrangements. U.S. GAAP prior to the issuance of ASU No. 2016-02 provided that lease arrangements meeting certain criteria were not recorded on an entity's balance sheet. ASU No. 2016-02 significantly changed the accounting for leases because a right-of-use ("ROU") model is now used whereby a lessee must record an ROU asset and a lease liability on its balance sheet for most of its leases. Under ASU No. 2016-02, leases are classified as either operating or financing arrangements, with such classification affecting the pattern of expense recognition in an entity's income statement. ASU No. 2016-02 also requires significantly expanded disclosures to meet the objective of enabling users of financial statements to assess the amount, timing and uncertainty of cash flows related to leases.

The Company adopted ASU No. 2016-02 on January 1, 2019 using a modified retrospective approach. We elected to use an available practical expedient that is permitted under ASU No. 2016-02 to record the required cumulative effect adjustments to the opening balance sheet in the period of adoption rather than in the earliest comparative period presented. As such, the Company's historical consolidated financial statements will not be restated. Certain other permitted practical expedients were used by the Company upon adoption of the standard, including: (i) combining lease and nonlease components as a single lease component for purposes of the recognition and measurement requirements under ASU No. 2016-02; (ii) not reassessing a lease arrangement to determine if its classification should be changed under ASU No. 2016-02; and (iii) not reassessing initial direct costs for leases that were in existence on January 1, 2019.

On adoption effective January 1, 2019, ASU No. 2016-02 will materially impact our consolidated balance sheets in the future because application of the ROU model yields a significant increase in both our assets and liabilities from our lease arrangements (all of which are operating leases) that have not previously been recorded on the Company’s consolidated balance sheets. We currently expect that the adoption of the standard will result in the recognition of operating lease liabilities ranging from $835.0 million to $855.0 million based on the present value of the Company’s remaining minimum lease payments, while the corresponding ROU assets will range from $637.0 million to $657.0 million. The Company’s consolidated statements of operations, stockholders' equity and cash flows will not be materially impacted by the adoption of the standard. The Company will provide the required disclosures under the standard in its Form 10-Q filing for the quarterly period ending March 31, 2019.

Accounting standards effective in 2020

Implementation Costs in a Cloud Computing Arrangement — In August 2018, the FASB issued ASU No. 2018-15, "Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract" ("ASU No. 2018-15"). ASU No. 2018-15 aligns the requirements for capitalizing implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. Costs that are capitalized under ASU No. 2018-15 will be expensed over the term of the cloud computing arrangement. ASU No. 2018-15 is effective for Gartner on January 1, 2020, with early adoption permitted. ASU No. 2018-15 may be adopted using either a retroactive or prospective method. The adoption of ASU No. 2018-15 is currently not expected to have a material impact on the Company's consolidated financial statements.

Defined Benefit Plan Disclosures — In August 2018, the FASB issued ASU No. 2018-14, "Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans" ("ASU No. 2018-14"). ASU No. 2018-14, which is part of the FASB's broader disclosure framework project, modifies and supplements the current U.S. GAAP annual disclosure requirements for employers that sponsor defined benefit pension plans. ASU No. 2018-14 is effective for Gartner for the year ending December 31, 2020, with early adoption permitted. ASU No. 2018-14 must be adopted on a retroactive basis and applied to each comparative period presented in an entity's financial statements. We are evaluating the potential impact of adopting ASU No. 2018-14; however, we do not currently expect it to have a material impact on the Company's consolidated financial statements.

Fair Value Measurement Disclosures — In August 2018, the FASB issued ASU No. 2018-13, "Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement" ("ASU No. 2018-13"). ASU No. 2018-13, which is part of the FASB's broader disclosure framework project, modifies and supplements the current U.S. GAAP disclosure requirements pertaining to fair value measurements, with an emphasis on Level 3 disclosures of the valuation hierarchy. ASU No. 2018-13 is effective for Gartner on January 1, 2020, with early adoption permitted. The adoption of ASU No. 2018-13 is currently not expected to have a material impact on the Company's consolidated financial statements.

Goodwill Impairment — In January 2017, the FASB issued ASU No. 2017-04, "Intangibles—Goodwill and Other - Simplifying the Test for Goodwill Impairment" ("ASU No. 2017-04"). ASU No. 2017-04 simplifies the determination of the amount of goodwill to be potentially charged off by eliminating Step 2 of the goodwill impairment test under current U.S. GAAP. ASU No. 2017-04 is effective for Gartner on January 1, 2020. The adoption of ASU No. 2017-04 is currently not expected to have a material impact on the Company's consolidated financial statements.

Financial Instrument Credit Losses — In June 2016, the FASB issued ASU No. 2016-13, "Financial Instruments—Credit Losses" ("ASU No. 2016-13"). ASU No. 2016-13 amends the current financial instrument impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables. ASU No. 2016-13 is effective for Gartner on January 1, 2020, with early adoption permitted. We are currently evaluating the potential impact of ASU No. 2016-13 on our consolidated financial statements.

The FASB continues to work on a number of other significant accounting standards which, if issued, could materially impact the Company's accounting policies and disclosures in future periods. As these standards have not yet been issued, the effective dates and potential impact are unknown.

Acquisitions and Divestiture

12 Months Ended

Dec. 31, 2018

Mergers, Acquisitions And Dispositions Disclosures [Abstract]

ACQUISITIONS AND DIVESTITURE

ACQUISITIONS AND DIVESTITURES

The Company accounts for business acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic 805, Business Combinations. The acquisition method of accounting requires the Company to record the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, with any excess of the consideration transferred over the estimated fair value of the net assets acquired, including identifiable intangible assets, to be recorded to goodwill. Under the acquisition method, the operating results of acquired companies are included in the Company's consolidated financial statements beginning on the date of acquisition.

The Company recognized $107.2 million, $158.5 million and $42.6 million of acquisition and integration charges in 2018, 2017 and 2016, respectively. Acquisition and integration charges reflect additional costs and expenses resulting from our acquisitions and include, among other items, professional fees, severance, stock-based compensation charges and accruals for exit costs for certain acquisition-related office space in Arlington, Virginia that the Company does not intend to occupy. During 2018, exit costs represented the single largest component of our acquisition and integration charges.

The table below presents a summary of the activity related to our accrual for exit costs at all of our facilities for the years ended December 31, 2018 and 2017 (in thousands). There was no such activity in 2016.



	2018			2017
Liability balance at beginning of the period	$	12,961		$	—
Charges and adjustments, net (1)	69,790			13,087
Payments, net of $2,515 in sublease rent during 2018	(26,087		)	(126		)
Liability balance at end of the period (2)	$	56,664		$	12,961


(1)	During 2018, the Company recognized $7.5 million of expense for changes in the original estimates of its exit cost obligations. The corresponding amount for 2017 was a benefit of $10.1 million.


(2)	In total, we estimate that the Company will make net cash payments of approximately $90.6 million for exit costs in connection with the activities described herein. Through December 31, 2018, in the aggregate, we have expensed $82.9 million and had net cash outlays of $26.2 million related to such activities.

Acquisitions

The Company did not have any business acquisitions in 2018.

2017

CEB

On April 5, 2017, the Company acquired 100% of the outstanding capital stock of CEB for an aggregate purchase price of $3.5 billion. The consideration transferred by Gartner included approximately $2.7 billion in cash and $818.7 million in fair value of Gartner common shares. CEB was a publicly-held company headquartered in Arlington, Virginia with approximately 4,900 employees. CEB's primary business was to serve as a leading provider of subscription-based, best practice research and analysis focusing on human resources, sales, finance, IT, and legal. CEB served executives and professionals at corporate and middle market institutions in over 70 countries.

On March 9, 2017, the Company acquired 100% of the outstanding capital stock of L2, a privately-held firm based in New York City with 150 employees, for an aggregate purchase price of $134.2 million. L2 is a subscription-based research business that benchmarks the digital performance of brands.

Total consideration transferred

The following table summarizes the aggregate consideration paid for these acquisitions during 2017 (in thousands):



Aggregate consideration (1):	CEB		L2		Total
Cash paid at close (2), (3)	$	2,687,704	$	134,199	$	2,821,903
Additional cash paid (2)	12,465		—		12,465
Fair value of Gartner equity (4)	818,660		—		818,660
Total	$	3,518,829	$	134,199	$	3,653,028


(1)	Includes the total consideration transferred for 100% of the outstanding capital stock of the acquired businesses.


(2)	The cash paid at close represents the gross contractual amount paid. The Company paid the additional $12.5 million in cash in third quarter 2017. Net of cash acquired and for cash flow reporting purposes, the Company paid a total of approximately $2.64 billion in cash for acquisitions in 2017.


(3)	The Company borrowed a total of approximately $2.8 billion in conjunction with the CEB acquisition (see Note 5 — Debt for additional information).


(4)	Consists of the fair value of (i) Gartner common stock issued (see Note 7 — Stockholders' Equity for additional information) and (ii) stock-based compensation replacement awards.

Allocation of Purchase Price

The following table summarizes the allocation of the purchase price to the fair value of the assets acquired and liabilities assumed for the acquisitions of L2 and CEB (in thousands):



	CEB (3)		L2 (4)		Total
Assets:
Cash	$	194,706	$	4,852	$	199,558
Fees receivable	175,440		8,277		183,717
Prepaid expenses and other current assets	53,610		1,167		54,777
Property, equipment and leasehold improvements	51,399		663		52,062
Goodwill (1)	2,349,589		108,202		2,457,791
Finite-lived intangible assets (2)	1,584,300		15,890		1,600,190
Other assets	66,818		13,067		79,885
Total assets	4,475,862		152,118		4,627,980
Liabilities:
Accounts payable and accrued liabilities	142,134		3,050		145,184
Deferred revenues (current)	246,472		13,200		259,672
Other liabilities	568,427		1,669		570,096
Total liabilities	957,033		17,919		974,952
Net assets acquired	$	3,518,829	$	134,199	$	3,653,028

(1)

The Company believes the goodwill resulting from the acquisitions is supportable based on anticipated synergies. For CEB, among the factors contributing to the anticipated synergies are a broader market presence, expanded product offerings and market opportunities, and an acceleration of CEB's growth by leveraging Gartner's global infrastructure and best practices in sales productivity and other areas. None of the recorded goodwill is expected to be deductible for tax purposes.

(2)

All of the acquired intangible assets are finite-lived. The determination of the fair value of the finite-lived intangible assets required management judgment and the consideration of a number of factors. In determining the fair values, management primarily relied on income valuation methodologies, in particular discounted cash flow models. The use of discounted cash flow models required the use of estimates, significant among them projected cash flows related to the particular asset; the useful lives of the particular assets; the selection of royalty and discount rates used in the models; and certain published industry benchmark data. In establishing the estimated useful lives of the finite-lived intangible assets, the Company relied on both internally-generated data for similar assets as well as certain published industry benchmark data. We believe the values we have assigned to the finite-lived intangible assets are both reasonable and supportable.

(3)

The Company's financial statements include the operating results of CEB beginning on April 5, 2017, the date of acquisition. CEB's operating results and the related goodwill are being reported as part of the Company's Research, Conferences and Other segments. Had the Company acquired CEB in prior periods, the impact to the Company's operating results would have been material, and as a result the following pro forma consolidated financial information is presented as if CEB had been acquired by the Company on January 1, 2016 (in thousands, except per share amounts):



	Twelve Months Ended
	December 31,
	2017		2016
Pro forma total revenue	$	3,726,470	$	3,183,070
Pro forma net income (loss)	150,167		(241,423		)
Pro forma basic and diluted income (loss) per share	$	1.66	$	(2.68	)

The pro forma results have been prepared in accordance with U.S. GAAP and include the following pro forma adjustments:

(a) An increase in interest expense and amortization of debt issuance costs related to the financing of the CEB acquisition. Note 5 — Debt provides further information regarding the Company's borrowings related to the CEB acquisition.

(b) A change in revenue as a result of the required fair value adjustment to deferred revenue.

(c) An adjustment for additional depreciation and amortization expense as a result of the purchase price allocation for finite-lived intangible assets and property, equipment, and leasehold improvements.

(4)

The Company's financial statements include the operating results of L2 beginning on March 9, 2017, the acquisition date. L2's operating results were not material to the Company's consolidated operating and segment results for 2017. Had the Company acquired L2 in prior periods, the impact to the Company's operating results would not have been material, and as a result pro forma financial information for L2 for prior periods has not been presented. L2's operating results and the related goodwill are being reported as part of the Company's Research segment.

2016

On November 9, 2016, the Company acquired 100% of the outstanding capital stock of Machina Research Limited ("Machina"), a privately-held firm based in London with 16 employees. The Company paid approximately $4.5 million in cash at close. Machina provides clients with subscription-based research that provides strategic insight and market intelligence in areas such as IOT ("internet of things").

On June 28, 2016, the Company acquired 100% of the outstanding capital stock of Newco 5CL Limited (which operates under the trade name "SCM World"), a privately-held firm based in London with 60 employees, for $34.2 million in cash paid at close. SCM World is a leading cross-industry peer network and learning community providing subscription-based research and conferences for supply chain executives. Net of cash acquired with the business and for cash flow reporting purposes, the Company paid approximately $27.9 million in cash for SCM World. The acquisition of SCM World also included an earn-out provision. The fair value of the earn-out was recorded on the acquisition date as part of the cost of the acquisition and was subsequently adjusted with a charge against earnings.

The Company recorded $32.4 million of goodwill and $5.9 million of amortizable intangible assets for these two acquisitions and an immaterial amount of other assets on a net basis. The operating results and the related goodwill are reported as part of the Company's Research and Conferences segments. The Company also recorded an additional $1.9 million of additional goodwill in 2016 related to a prior year acquisition.

Divestitures

During 2018, the Company completed the divestiture of all three of the non-core businesses comprising its Other segment, all of which were acquired in the CEB acquisition in April 2017. These three businesses contributed approximately $97.3 million of revenue and $60.5 million of gross contribution in 2018. The Company used the cash proceeds from these divestitures to pay down outstanding debt.

Additional information regarding the Other segment divestitures is provided below:

CEB Challenger training business

On August 31, 2018, the Company sold its CEB Challenger training business for $119.1 million and realized approximately $116.0 million in cash, which is net of working capital adjustments and certain closing costs. The Company recorded a pretax gain on the sale of approximately $8.3 million.

CEB Workforce Survey and Analytics business

On May 1, 2018, the Company sold its CEB Workforce Survey and Analytics business for $28.0 million and realized approximately $26.4 million in cash, which is net of certain closing expenses. The Company recorded a pretax gain on the sale of approximately $8.8 million.

CEB Talent Assessment business

On April 3, 2018, the Company sold its CEB Talent Assessment business for $403.0 million and realized approximately $375.8 million in cash from the sale, which is net of cash transferred with the business and certain closing expenses. The Company recorded a pretax gain of approximately $15.5 million on the sale.

Other asset sales

During 2018, the Company also received $8.6 million in cash proceeds as well as other consideration and recorded a net pretax gain of approximately $12.8 million from the sale of certain non-core assets acquired in the CEB transaction. This includes the October 31, 2018 sale of a small Research segment product called Metrics That Matter.

Other Assets

12 Months Ended

Dec. 31, 2018

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

OTHER ASSETS

Other assets consist of the following (in thousands):



	December 31,
	2018		2017
Benefit plan-related assets	$	75,653	$	97,525
Non-current deferred tax assets	34,494		31,067
Other	46,222		65,150
Total other assets	$	156,369	$	193,742

Accounts Payable, Accrued, and Other Liabilities

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

ACCOUNTS PAYABLE, ACCRUED, AND OTHER LIABILITIES

Accounts payable and accrued liabilities consist of the following (in thousands):



	December 31,
	2018		2017
Accounts payable	$	37,508	$	49,000
Payroll and employee benefits payable	143,803		120,278
Severance and retention bonus payable	28,292		44,685
Bonus payable	170,719		162,710
Commissions payable	126,844		108,969
Taxes payable	19,725		46,758
Other accrued liabilities	183,222		134,421
Total accounts payable and accrued liabilities	$	710,113	$	666,821

Other liabilities consist of the following (in thousands):



	December 31,
	2018		2017
Non-current deferred revenue	$	21,194	$	16,205
Long-term taxes payable	66,304		66,386
Benefit plan-related liabilities	96,033		118,868
Lease-related matters	165,374		115,840
Non-current deferred tax liabilities	214,687		206,338
Other	50,081		54,362
Total other liabilities	$	613,673	$	577,999

Debt

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

DEBT

2016 Credit Agreement

The Company entered into a term loan and revolving credit facility on June 17, 2016 (the "2016 Credit Agreement"). As discussed below, the 2016 Credit Agreement was amended three times during 2017 in conjunction with the acquisition of CEB. The 2016 Credit Agreement, as amended, provided for a $1.5 billion Term loan A facility, a $500.0 million Term loan B facility and a $1.2 billion revolving credit facility. The 2016 Credit Agreement contains certain customary restrictive loan covenants, including, among others, financial covenants that apply a maximum leverage ratio and a minimum interest expense coverage ratio, and covenants limiting Gartner’s ability to incur indebtedness, grant liens, make acquisitions, merge, dispose of assets, pay dividends, repurchase stock, make investments and enter into certain transactions with affiliates. The Company was in full compliance with the covenants as of December 31, 2018.

In 2017 the Company borrowed a total of approximately $2.8 billion for the CEB acquisition. The Company borrowed $1.675 billion under the 2016 Credit Agreement, which consisted of $900.0 million under an increased Term loan A facility, $500.0 million under a new Term loan B facility and $275.0 million on an existing revolving credit facility. The $1.675 billion drawn under the 2016 Credit Agreement, along with the funds raised through the issuance of $800.0 million Senior Notes and a $300.0 million 364-day Bridge Credit Facility, were used to fund the CEB acquisition and related costs. The funds borrowed under the 364-day Bridge Credit Facility were completely repaid during 2017 and the borrowings under the Term loan B facility were completely repaid during 2018.

On January 20, 2017, the Company entered into a first amendment to the 2016 Credit Agreement, which was entered into to permit the acquisition of CEB and the incurrence of additional debt to finance, in part, the acquisition and repay certain debt of CEB, and to modify certain covenants. On March 20, 2017, the Company entered into a second amendment to the 2016 Credit Agreement. The second amendment was also entered into in connection with the acquisition of CEB and was executed primarily to extend the maturity date of the Term loan A facility and the revolving credit facility through March 20, 2022 and to revise the interest rate and amortization schedule. On April 5, 2017, in conjunction with the closing of the CEB acquisition, the Company entered into a third amendment to the 2016 Credit Agreement, which increased the aggregate principal amount of the existing Term loan A facility by $900.0 million and added the Term loan B facility in an aggregate principal amount of $500.0 million.

The Term loan A facility is being repaid in 16 consecutive quarterly installments that commenced on June 30, 2017, plus a final payment to be made on March 20, 2022. The additional amount drawn under the Term loan A facility during 2017 has the same maturity date and is subject to the same interest, repayment terms, amortization schedules, representations and warranties, affirmative and negative covenants and events of default as the amounts outstanding under such facility prior to entry by the Company into the third amendment. The revolving credit facility may be borrowed, repaid, and re-borrowed through March 20, 2022, at which time all amounts must be repaid. Amounts borrowed under the Term loan A facility and the revolving credit facility bear interest at a rate equal to, at the Company's option, either:

(i) the greatest of: (x) the Administrative Agent’s prime rate; (y) the rate calculated by the New York Federal Reserve Bank for federal funds transactions plus 1/2 of 1%; and (z) the eurodollar rate (adjusted for statutory reserves) plus 1%, in each case plus a margin equal to between 0.125% and 1.50%, depending on Gartner’s consolidated leverage ratio as of the end of the four consecutive fiscal quarters most recently ended; or

(ii) the eurodollar rate (adjusted for statutory reserves) plus a margin equal to between 1.125% and 2.50%, depending on Gartner’s leverage ratio as of the end of the four consecutive fiscal quarters most recently ended.

During 2018 the Company repaid the entire $496.3 million outstanding under the Term loan B facility. The Term loan B facility was scheduled to mature on April 5, 2024 and the amounts outstanding thereunder bore interest at a rate per annum equal to, at the option of Gartner, (i) adjusted LIBOR plus 2.00% or (ii) an alternate base rate plus 1.00%.

364-day Bridge Credit Facility

On April 5, 2017, the Company entered into a senior unsecured 364-day Bridge Credit Facility in an aggregate principal amount of $300.0 million, which was immediately drawn down to fund a portion of the purchase price associated with the CEB acquisition. The Company repaid the entire $300.0 million of the 364-day Bridge Credit Facility during 2017.

Senior Notes

On March 30, 2017, the Company issued $800.0 million aggregate principal amount of 5.125% Senior Notes due 2025 (the “Senior Notes”). The proceeds of the Senior Notes were used to fund a portion of the purchase price associated with the CEB acquisition.

The Senior Notes were issued at an issue price of 100.0% and bear interest at a fixed rate of 5.125% per annum. Interest on the Senior Notes is payable on April 1 and October 1 of each year. The Senior Notes mature on April 1, 2025. The Company may redeem some or all of the Senior Notes at any time on or after April 1, 2020 for cash at the redemption prices set forth in the Note Indenture, plus accrued and unpaid interest to, but not including, the redemption date. Prior to April 1, 2020, the Company may redeem up to 40% of the aggregate principal amount of the Senior Notes with the proceeds of certain equity offerings at a redemption price of 105.125% plus accrued and unpaid interest to, but not including, the redemption date. In addition, the Company may redeem some or all of the Senior Notes prior to April 1, 2020 at a redemption price of 100% of the principal amount of the Senior Notes plus accrued and unpaid interest to, but not including, the redemption date, plus a “make-whole” premium. If the Company experiences certain kinds of changes of control, it will be required to offer to purchase the Senior Notes at a price equal to 101% of the principal amount thereof plus accrued and unpaid interest.

The Senior Notes are the Company’s general unsecured senior obligations, and are effectively subordinated to all of the Company’s existing and future secured indebtedness to the extent of the value of the collateral securing such indebtedness, structurally subordinated to all existing and future indebtedness and other liabilities of the Company’s non-guarantor subsidiaries, equal in right of payment to all of the Company’s and Company’s guarantor subsidiaries’ existing and future senior indebtedness and senior in right of payment to all of the Company’s future subordinated indebtedness, if any.

Outstanding Borrowings

The following table summarizes the Company’s total outstanding borrowings (in thousands):



	December 31,
Description:	2018			2017
2016 Credit Agreement - Term loan A facility (1)	$	1,355,062		$	1,429,312
2016 Credit Agreement - Term loan B facility (2)	—			496,250
2016 Credit Agreement - Revolving credit facility (1), (3)	155,000			595,000
Senior notes (4)	800,000			800,000
Other (5)	2,030			2,500
Principal amount outstanding (6), (7)	2,312,092			3,323,062
Less: deferred financing fees (8)	(30,405		)	(44,217		)
Net balance sheet carrying amount	$	2,281,687		$	3,278,845


(1)	The contractual annualized interest rate as of December 31, 2018 on the Term loan A facility and the revolving credit facility was 4.02%, which consisted of a floating eurodollar base rate of 2.52% plus a margin of 1.50%. However, the Company has interest rate swap contracts that effectively convert the floating eurodollar base rates on amounts outstanding to a fixed base rate.


(2)	The Term loan B facility was completely repaid in 2018.


(3)	The Company had $1.0 billion of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2018.


(4)	Consists of $800.0 million principal amount of Senior Notes outstanding. The Senior Notes pay a fixed rate of 5.125% and mature on April 1, 2025.


(5)	Consists of a State of Connecticut economic development loan with a 3.00% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. The loan may be repaid at any time by the Company without penalty.


(6)	The weighted average annual effective rate on the Company's total debt outstanding for 2018, including the effects of its interest rate swaps discussed below, was 4.17%.


(7)	The contractual due dates of principal amounts by year on the debt outstanding as of December 31, 2018 were as follows: $102.6 million in 2019; $139.7 million in 2020; $37.6 million in 2021; $1.23 billion in 2022; and $800.0 million in 2025.

(8)

Deferred financing fees are being amortized to Interest expense over the term of the related debt obligation. The Company wrote off approximately $6.9 million of deferred financing fees in 2018 related to the repayment of the Term loan B facility. During 2017, the Company paid $51.2 million in additional deferred financing fees and recorded a charge of approximately $6.1 million for the write-off of deferred financing fees related to the prior financing arrangement.

Interest Rate Swaps

The Company has five active fixed-for-floating interest rate swap contracts with a total notional value of $1.4 billion that mature through 2022. The Company designates the swaps as accounting hedges of the forecasted interest payments on $1.4 billion of the Company’s variable-rate borrowings. The Company pays base fixed rates on these swaps ranging from 1.53% to 2.13% and in return receives a floating eurodollar base rate on 30-day notional borrowings. The Company has also entered into two additional forward-starting, fixed-for-floating interest rate swap contracts with a combined notional value of $700.0 million that will hedge a portion of the Company's variable-rate borrowings upon the maturity of three of the currently active swap contracts in late 2019.

The Company accounts for the interest rate swap contracts as cash flow hedges in accordance with FASB ASC Topic 815. Since the swaps hedge forecasted interest payments, changes in the fair value of the swaps are recorded in accumulated other comprehensive income (loss), a component of equity, as long as the swaps continue to be highly effective hedges of the designated interest rate risk. Any ineffective portion of a change in the fair value of the hedges is recorded in earnings. All of the Company's swaps were considered highly effective hedges of the forecasted interest payments as of both December 31, 2018 and 2017. The interest rate swaps had a net negative fair value (liability) of $10.7 million as of December 31, 2018 and a net positive fair value (asset) of $3.4 million as of December 31, 2017. Such amounts were deferred and recorded in Accumulated other comprehensive (loss) income, net of tax effect.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Contractual Lease Commitments. The Company leases various facilities, computer and office equipment, furniture, and other assets under non-cancelable operating lease agreements expiring between 2019 and 2038. Future minimum annual cash payments under those operating lease agreements as of December 31, 2018 were as follows (in thousands):



Year ended December 31,
2019	$	130,991
2020	121,802
2021	118,945
2022	111,117
2023	106,113
Thereafter	689,360
Total minimum lease payments (1)	$	1,278,328

(1) Excludes approximately $372.0 million of sublease income.

Legal Matters. The Company is involved in legal proceedings and litigation arising in the ordinary course of business. We believe that the potential liability, if any, in excess of amounts already accrued from all proceedings, claims and litigation will not have a material effect on our financial position, cash flows or results of operations when resolved in a future period.

Indemnifications. The Company has various agreements that may obligate us to indemnify the other party with respect to certain matters. Generally, these indemnification clauses are included in contracts arising in the normal course of business under which we customarily agree to hold the other party harmless against losses arising from a breach of representations related to such matters as title to assets sold and licensed or certain intellectual property rights. It is not possible to predict the maximum potential amount of future payments under these indemnification agreements due to the conditional nature of the Company’s obligations and the unique facts of each particular agreement. Historically, payments made by us under these agreements have not been material. As of December 31, 2018, the Company did not have any material payment obligations under any such indemnification agreements.

Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

STOCKHOLDERS’ EQUITY

Common stock. Holders of Gartner’s Common Stock, par value $.0005 per share (“Common Stock”) are entitled to one vote per share on all matters to be voted by stockholders. The Company does not currently pay cash dividends on its Common Stock. Also, our 2016 Credit Agreement contains a negative covenant that may limit our ability to pay dividends. The following table summarizes transactions relating to our Common Stock for the three years ended December 31, 2018:



	Issued Shares	Treasury Stock Shares
Balance at December 31, 2015	156,234,415	73,896,245
Issuances under stock plans	—	(923,696	)
Purchases for treasury (1)	—	610,623
Balance at December 31, 2016	156,234,415	73,583,172
Issued in connection with the acquisition of CEB	7,367,652	—
Issuances under stock plans	—	(1,186,150	)
Purchases for treasury (1)	—	382,183
Balance at December 31, 2017	163,602,067	72,779,205
Issuances under stock plans	—	(933,246	)
Purchases for treasury (1), (2)	—	2,054,018
Balance at December 31, 2018	163,602,067	73,899,977


(1)	The Company used a total of $260.8 million, $41.3 million and $59.0 million in cash for share repurchases in 2018, 2017 and 2016, respectively.


(2)	The number of shares repurchased in 2018 includes shares repurchased in December 2018 that settled in January 2019.

Share Issuance Related to the Acquisition of CEB. On April 5, 2017, the Company issued 7.4 million of its common shares at a fair value of $109.65 per common share as part of the consideration for the CEB acquisition. Note 2 — Acquisitions and Divestitures provides additional information regarding the CEB acquisition. The fair value of the Company's common stock was determined based on an average of the high and low prices of the common stock as reported by the New York Stock Exchange on April 5, 2017, the date of the acquisition.

Share repurchase authorization. The Company has a $1.2 billion board authorization adopted in May 2015 to repurchase the Company's common stock, of which $0.9 billion remained available as of December 31, 2018. The Company may repurchase its common stock from time-to-time in amounts, at prices and in the manner that the Company deems appropriate, subject to the availability of stock, prevailing market conditions, the trading price of the stock, the Company’s financial performance and other conditions. Repurchases may be made through open market purchases (which may include repurchase plans designed to comply with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended), accelerated share repurchases, private transactions or other transactions and will be funded from cash on hand and borrowings under our 2016 Credit Agreement.

Accumulated Other Comprehensive Income (Loss), Net. The following tables disclose information about changes in Accumulated Other Comprehensive Income (Loss) ("AOCI/L") by component and the related amounts reclassified out of AOCI/L to income during the years indicated (net of tax, in thousands) (1):

2018



	Interest Rate Swaps			Defined Benefit Pension Plans			Foreign Currency Translation Adjustments			Total
Balance - December 31, 2017	$	2,483		$	(5,861	)	$	4,886		$	1,508
Adoption of ASU No. 2018-02 (2)	591			—			—			591
Other comprehensive income (loss) activity during the period:
Change in AOCI/L before reclassifications to income	(9,447		)	—			29,066			19,619
Reclassifications from AOCI/L to income (3), (4), (5)	(1,397		)	123			(60,311		)	(61,585		)
Other comprehensive income (loss) for the period	(10,844		)	123			(31,245		)	(41,966		)
Balance - December 31, 2018	$	(7,770	)	$	(5,738	)	$	(26,359	)	$	(39,867	)

2017



	Interest Rate Swaps			Defined Benefit Pension Plans			Foreign Currency Translation Adjustments			Total
Balance - December 31, 2016	$	(1,409	)	$	(5,797	)	$	(42,477	)	$	(49,683	)
Other comprehensive income (loss) activity during the period:
Change in AOCI/L before reclassifications to income	(1,492		)	—			47,363			45,871
Reclassifications from AOCI/L to income (3), (4)	5,384			(64		)	—			5,320
Other comprehensive income (loss) for the period	3,892			(64		)	47,363			51,191
Balance - December 31, 2017	$	2,483		$	(5,861	)	$	4,886		$	1,508

(1) Amounts in parentheses represent debits (deferred losses).

(2) See Note 1 - Business and Significant Accounting Policies for additional information regarding the Company's adoption of ASU No. 2018-02.

(3) The reclassifications related to interest rate swaps (cash flow hedges) were recorded in Interest expense, net of tax effect. See Note 11 – Derivatives and Hedging for information regarding the hedges.

(4) The reclassifications related to defined benefit pension plans were primarily recorded in Selling, general and administrative expense, net of tax effect. See Note 13 – Employee Benefits for information regarding the Company’s defined benefit pension plans.

(5) The reclassification related to foreign currency translation adjustments in 2018 was recorded in Gain from divested operations. See Note 2 – Acquisitions and Divestitures for information regarding our divestitures in 2018.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

STOCK-BASED COMPENSATION

The Company grants stock-based compensation awards as an incentive for employees and directors to contribute to the Company’s long-term success. The Company currently awards stock-settled stock appreciation rights, service-based and performance-based restricted stock units, and common stock equivalents. As of December 31, 2018, the Company had 4.9 million shares of its common stock, par value $.0005 per share, (the "Common Stock") available for stock-based compensation awards under its 2014 Long-Term Incentive Plan.

The Company accounts for stock-based compensation awards in accordance with FASB ASC Topics 505 and 718 and SEC Staff Accounting Bulletins No. 107 and No. 110. Stock-based compensation expense for equity awards is based on the fair value of the award on the date of grant. The Company recognizes stock-based compensation expense over the period that the related service is performed, which is generally the same as the vesting period of the underlying award. Currently, the Company issues treasury shares upon the exercise, release or settlement of stock-based compensation awards.

Determining the appropriate fair value model and calculating the fair value of stock-based compensation awards requires the use of certain subjective assumptions, including the expected life of a stock-based compensation award and Common Stock price volatility. In addition, determining the appropriate periodic stock-based compensation expense requires management to estimate the likelihood of the achievement of certain performance targets. The assumptions used in calculating the fair values of stock-based compensation awards and the related periodic expense represent management’s best estimates, which involve inherent uncertainties and the application of judgment. As a result, if circumstances change and the Company deems it necessary in the future to modify the assumptions it made or to use different assumptions, or if the quantity and nature of the Company’s stock-based compensation awards changes, then the amount of expense may need to be adjusted and future stock-based compensation expense could be materially different from what has been recorded in the current period.

Stock-Based Compensation Expense

The Company recognized the following stock-based compensation expense by award type and expense category line item during the years ended December 31 (in millions):



Award type	2018		2017		2016
Stock appreciation rights	$	6.3	$	5.6	$	5.6
Restricted stock units	59.2		72.6		40.4
Common stock equivalents	0.7		0.7		0.7
Total (1)	$	66.2	$	78.9	$	46.7



Expense category line item	2018		2017		2016
Cost of services and product development	$	28.1	$	25.8	$	21.9
Selling, general and administrative	36.2		35.5		24.8
Acquisition and integration charges (2)	1.9		17.6		—
Total (1)	$	66.2	$	78.9	$	46.7


(1)	Includes charges of $19.4 million, $22.9 million and $19.4 million during 2018, 2017 and 2016, respectively, for awards to retirement-eligible employees. Those awards vest on an accelerated basis.


(2)	These charges are the result of (i) the acceleration of the vesting of certain restricted stock units related to the CEB acquisition and (ii) restricted stock units granted in connection with the CEB integration process.

As of December 31, 2018, the Company had $79.1 million of total unrecognized stock-based compensation cost, which is expected to be expensed over the remaining weighted average service period of approximately 2.3 years.

Stock-Based Compensation Awards

The disclosures presented below provide information regarding the Company’s stock-based compensation awards, all of which have been classified as equity awards in accordance with FASB ASC Topic 505.

Stock Appreciation Rights

Stock-settled stock appreciation rights ("SARs") permit the holder to participate in the appreciation of the value of the Common Stock. After the applicable vesting criteria have been satisfied, SARs are settled in shares of Common Stock upon exercise by the employee. SARs vest ratably over a four-year service period and expire seven years from the date of grant. The fair value of a SARs award is recognized as compensation expense on a straight-line basis over four years. SARs have only been awarded to the Company’s executive officers.

When SARs are exercised, the number of shares of Common Stock issued is calculated as follows: (1) the total proceeds from the exercise of the SARs award (calculated as the closing price of the Common Stock as reported on the New York Stock Exchange on the date of exercise less the exercise price of the SARs award, multiplied by the number of SARs exercised) is divided by (2) the closing price of the Common Stock on the date of exercise. The Company withholds a portion of the shares of the Common Stock issued upon exercise to satisfy statutory tax withholding requirements. SARs recipients do not have any stockholder rights until the shares of Common Stock are issued in respect of the award, which is subject to the prior satisfaction of the vesting and other criteria relating to such grants.

The following table summarizes changes in SARs outstanding during the year ended December 31, 2018:



	Stock Appreciation Rights ("SARs") (in millions)		Per Share Weighted Average Exercise Price		Per Share Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (Years)
Outstanding at December 31, 2017	1.2		$	76.73	$	17.35	4.28
Granted	0.3		114.26		25.63		6.11
Exercised	(0.3	)	60.67		15.10		n/a
Outstanding at December 31, 2018 (1) (2)	1.2		$	89.45	$	19.88	4.33
Vested and exercisable at December 31, 2018 (2)	0.5		$	75.73	$	17.02	3.24

n/a = not applicable


(1)	As of December 31, 2018, 0.7 million of the total SARs outstanding were unvested. The Company expects that substantially all of those unvested awards will vest in future periods.


(2)	As of December 31, 2018, the total SARs outstanding had an intrinsic value of $46.0 million. On such date, SARs vested and exercisable had an intrinsic value of $26.9 million.

The fair value of a SARs award is determined on the date of grant using the Black-Scholes-Merton valuation model with the following weighted average assumptions for the years ended December 31:



	2018		2017		2016
Expected dividend yield (1)	—	%	—	%	—	%
Expected stock price volatility (2)	21	%	22	%	22	%
Risk-free interest rate (3)	2.5	%	1.8	%	1.1	%
Expected life in years (4)	4.52		4.53		4.39


(1)	The expected dividend yield assumption was based on both the Company's historical and anticipated dividend payouts. Historically, the Company has not paid cash dividends on its Common Stock.


(2)	The determination of expected stock price volatility was based on both historical Common Stock prices and implied volatility from publicly traded options in the Common Stock.


(3)	The risk-free interest rate was based on the yield of a U.S. Treasury security with a maturity similar to the expected life of the award.


(4)	The expected life represents the Company’s estimate of the weighted average period of time the SARs are expected to be outstanding (that is, the period between the service inception date and the expected exercise date).

Restricted Stock Units

Restricted stock units ("RSUs") give the awardee the right to receive shares of Common Stock when the vesting conditions are met and certain restrictions lapse. Each RSU that vests entitles the awardee to one share of Common Stock. RSU awardees do not have any of the rights of a Gartner stockholder, including voting rights and the right to receive dividends and distributions, until the shares are released. The fair value of a RSU award is determined on the date of grant based on the closing price of the Common Stock as reported on the New York Stock Exchange on that date. Service-based RSUs vest ratably over four years and are expensed on a straight-line basis over the vesting period. Performance-based RSUs are subject to the satisfaction of both performance and service conditions, vest ratably over four years and are expensed on an accelerated basis over the vesting period.

The following table summarizes the changes in RSUs outstanding during the year ended December 31, 2018:



	Restricted Stock Units ("RSUs") (in millions)		Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2017	1.5		$	91.47
Granted (1)	0.7		112.96
Vested and released	(0.7	)	88.69
Forfeited	(0.1	)	104.95
Outstanding at December 31, 2018 (2) (3)	1.4		$	101.75

(1)

The 0.7 million of RSUs granted during 2018 consisted of 0.3 million of performance-based RSUs awarded to executives and 0.4 million of service-based RSUs awarded to non-executive employees and non-management board members. The performance-based awards include RSUs in final settlement of 2017 grants and approximately 0.2 million of RSUs representing the target amount of the grant for 2018 that is tied to an increase in Gartner’s total contract value for such year. The number of performance-based RSUs for 2018 that could have been earned ranged from 0% to 200% of the target amount. The actual increase in Gartner’s total contract value for 2018 as measured on December 31, 2018 yielded approximately 144% of the target amount. The incremental awards based on the actual achievement under the 2018 grant will be issued in 2019.


(2)	The Company expects that substantially all of the RSUs outstanding will vest in future periods.


(3)	As of December 31, 2018, the weighted average remaining contractual term of the RSUs outstanding was approximately 1.1 years.

Common Stock Equivalents

Common stock equivalents ("CSEs") are convertible into Common Stock. Each CSE entitles the holder to one share of Common Stock. Members of our Board of Directors receive their directors’ fees in CSEs unless they opt to receive up to 50% of those fees in cash. Generally, CSEs have no defined term and are converted into shares of Common Stock when service as a director terminates unless the director has elected an accelerated release. The fair value of a CSE award is determined on the date of grant based on the closing price of the Common Stock as reported on the New York Stock Exchange on that date. CSEs vest immediately and, as a result, they are recorded as expense on the date of grant.

The following table summarizes the changes in CSEs outstanding during the year ended December 31, 2018:



	Common Stock Equivalents ("CSEs")		Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2017	110,013		$	23.19
Granted	5,550		131.49
Converted to shares of Common Stock upon grant	(5,783	)	93.45
Outstanding at December 31, 2018	109,780		$	24.96

Employee Stock Purchase Plan

The Company has an employee stock purchase plan (the “ESP Plan”) wherein eligible employees are permitted to purchase shares of Common Stock through payroll deductions, which may not exceed 10% of an employee’s compensation, or $23,750 in any calendar year, at a price equal to 95% of the closing price of the Common Stock as reported on the New York Stock Exchange at the end of each offering period. As of December 31, 2018, the Company had 0.7 million shares available for purchase under the ESP Plan. The ESP Plan is considered non-compensatory under FASB ASC Topic 718 and, as a result, the Company does not record stock-based compensation expense for employee share purchases. The Company received $14.7 million, $11.7 million and $9.3 million in cash from employee share purchases under the ESP Plan during 2018, 2017 and 2016, respectively.

Computation of Earnings Per Share

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

COMPUTATION OF EARNINGS PER SHARE

Basic earnings per share (“EPS”) is computed by dividing net income by the weighted average number of shares of Common Stock outstanding for the period. Diluted EPS reflects the potential dilution of securities that could share in earnings. When the impact of common share equivalents is anti-dilutive, they are excluded from the calculation.

The following table sets forth the calculation of basic and diluted earnings per share for the three years ended December 31 (in thousands, except per share data):



	2018		2017		2016
Numerator:
Net income used for calculating basic and diluted earnings per common share	$	122,456	$	3,279	$	193,582
Denominator: (1)
Weighted average common shares used in the calculation of basic earnings per share	90,827		88,466		82,571
Common share equivalents associated with stock-based compensation plans	1,295		1,324		1,249
Shares used in the calculation of diluted earnings per share	92,122		89,790		83,820
Earnings per share: (2)
Basic	$	1.35	$	0.04	$	2.34
Diluted	$	1.33	$	0.04	$	2.31


(1)	The Company repurchased 2.1 million, 0.4 million and 0.6 million shares of its Common Stock in 2018, 2017 and 2016, respectively.


(2)	Both basic and diluted earnings per share for 2017 include a tax benefit of approximately $0.66 per share related to the U.S. Tax Cuts and Jobs Act of 2017. Note 10 — Income Taxes provides information about the Company's income taxes.

The following table presents the number of common share equivalents that were not included in the computation of diluted earnings per share in the above table because the effect would have been anti-dilutive. During periods with net income, these common share equivalents were anti-dilutive because their exercise price was greater than the average market value of a share of Common Stock during the period.



	2018		2017		2016
Anti-dilutive common share equivalents as of December 31 (in millions): (a)	—		0.3		0.2
Average market price per share of Common Stock during the year	$	135.60	$	116.09	$	92.58

(a) Anti-dilutive common shares for 2018 were minimal.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

INCOME TAXES

The following is a summary of the components of the Company's income (loss) before income taxes for the years ended December 31 (in thousands):



	2018		2017			2016
U.S.	$	34,159	$	(135,757	)	$	182,178
Non-U.S.	146,962		7,940			106,253
Income (loss) before income taxes	$	181,121	$	(127,817	)	$	288,431

The expense (benefit) for income taxes on the above income consists of the following components (in thousands):



	2018			2017			2016
Current tax expense:
U.S. federal	$	2,817		$	48,339		$	58,616
State and local	6,969			434			11,292
Foreign	45,042			38,602			27,536
Total current	54,828			87,375			97,444
Deferred tax (benefit) expense:
U.S. federal	12,462			(176,046		)	(61		)
State and local	1,258			(14,363		)	(349		)
Foreign	(13,795		)	(25,898		)	(1,626		)
Total deferred	(75		)	(216,307		)	(2,036		)
Total current and deferred	54,753			(128,932		)	95,408
Benefit (expense) relating to interest rate swaps used to increase (decrease) equity	3,840			(2,477		)	(1,113		)
Benefit from stock transactions with employees used to increase equity	58			46			52
Benefit relating to defined-benefit pension adjustments used to increase equity	14			267			502
Total tax expense (benefit)	$	58,665		$	(131,096	)	$	94,849

Long-term deferred tax assets and liabilities are comprised of the following (in thousands):



	December 31,
	2018			2017
Accrued liabilities	$	96,292		$	80,557
Loss and credit carryforwards	14,830			59,502
Assets relating to equity compensation	19,653			24,874
Other assets	14,092			30,236
Gross deferred tax assets	144,867			195,169
Property, equipment, and leasehold improvements	(3,421		)	(962		)
Intangible assets	(214,580		)	(372,542		)
Prepaid expenses	(41,926		)	(35,126		)
Other liabilities	(61,068		)	(6,584		)
Gross deferred tax liabilities	(320,995		)	(415,214		)
Valuation allowance	(4,066		)	(3,192		)
Net deferred tax liabilities	$	(180,194	)	$	(223,237	)

Net deferred tax assets and net deferred tax liabilities were $34.5 million and $214.7 million as of December 31, 2018, respectively, and $30.5 million and $253.7 million as of December 31, 2017, respectively. These amounts are reported in Other assets and Other liabilities in the Consolidated Balance Sheets. Management has concluded it is more likely than not that the reversal of deferred tax liabilities and results of future operations will generate sufficient taxable income to realize the deferred tax assets, net of the valuation allowance at December 31, 2018.

The valuation allowances of $4.1 million as of December 31, 2018 and $3.2 million as of December 31, 2017, primarily relate to net operating losses which are not likely to be realized.

As of December 31, 2018, the Company had state and local tax net operating loss carryforwards of $35.2 million, of which $0.1 million expires within one to five years and $3.5 million expires within six to fifteen years and $31.6 million expires within sixteen to twenty years. The Company also had state tax credits of $2.2 million, a majority of which will expire in five to six years. As of December 31, 2018, the Company had non-U.S. net operating loss carryforwards of $5.0 million, of which $0.1 million expires over the next 20 years and $4.9 million can be carried forward indefinitely. These amounts have been reduced for associated unrecognized tax benefits, consistent with ASU No. 2013-11, "Income Taxes—Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists."

The differences between the U.S. federal statutory income tax rate and the Company’s effective tax rate on income before income taxes for the years ended December 31 follow:



	2018		2017		2016
Statutory tax rate	21.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	—		3.6		2.3
Effect of non-U.S. operations	(10.6	)	5.9		(6.1	)
Change in the reserve for tax contingencies	15.7		(2.8	)	3.2
Law changes	(1.3	)	41.8		—
Stock-based compensation expense	(5.3	)	11.0		(3.8	)
Nondeductible acquisition costs	0.9		(7.9	)	2.6
Nondeductible meals and entertainment costs	2.7		(3.5	)	1.1
Gains/Losses on divested operations and held-for-sale assets	12.2		13.1		—
Limitation on executive compensation	2.7		(0.1	)	—
Foreign-derived intangible income	(2.0	)	—		—
Change in the valuation allowance	0.5		3.0		(0.2	)
Goodwill	(3.8	)	—		—
Other items, net	(0.3	)	3.5		(1.2	)
Effective tax rate	32.4	%	102.6	%	32.9	%

The U.S. Tax Cuts and Jobs Act (the "Act”) was enacted on December 22, 2017. Among other things, the Act reduces the U.S. federal corporation tax rate from 35% to 21%, requires companies to pay a one-time transition tax on accumulated deferred foreign income (“ADFI”) of foreign subsidiaries that were previously tax deferred and creates a new tax on global intangible low-taxed income (“GILTI”) attributable to foreign subsidiaries. As of December 31, 2018, we have completed our accounting for the tax effects of enactment of the Act.

We remeasured U.S. deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. We reduced our income tax expense by $13.8 and $123.2 million in 2018 and 2017, respectively for this item.

The tax on ADFI is based on our total post-1986 earnings and profits ("E&P") of our foreign subsidiaries that were previously deferred from U.S. income taxes. We increased income tax expense by $8.4 million and $63.6 million in 2018 and 2017, respectively, for this one-time transition tax liability. Significant foreign tax credit and net operating loss carryovers will be utilized to reduce the transition tax liability. The Company has elected to pay the remaining cash tax liability of approximately $10.0 million over 8 years as permitted by the Act.

The Act also created a new tax on GILTI attributable to foreign subsidiaries. Companies have the option to account for the GILTI tax as a period cost in the period incurred, or to recognize deferred taxes for temporary differences including outside basis differences expected to reverse as a result of the GILTI provisions. The Company has elected to account for the GILTI tax as a period cost in the period incurred.

Various provisions of the Act are highly complex and remains unclear in certain respects. Additional guidance in the form of notices and proposed regulations have been issued, and further guidance is expected to be issued. Changes could be made to the proposed regulations, future legislation could be enacted, and more regulations and notices could be issued. We will continue to monitor and will reflect impacts in future financial statements as appropriate. In addition, many state and local tax jurisdictions are still determining how they will interpret the Act. Final state and local governments’ legislation or guidance relating to the Act may impact our financial results.

In July 2015, the United States Tax Court (the “Court”) issued an opinion relating to the treatment of stock-based compensation

expense in an inter-company cost-sharing arrangement. In its opinion, the Court held that affiliated companies may exclude stock-based compensation expense from their cost-sharing arrangement. The Internal Revenue Service is appealing the decision. Because of uncertainty related to the final resolution of this litigation and the recognition of potential benefits to the Company, the Company has not recorded any financial statement benefit related to open statute years associated with this matter. The Company will monitor developments related to this case and the potential impact of those developments on the Company’s consolidated financial statements.

As of December 31, 2018 and 2017, the Company had unrecognized tax benefits of $90.3 million and $60.3 million, respectively. The increase is primarily attributable to positions taken with respect to intercompany transactions, taxable E&P, and state income tax positions. The unrecognized tax benefits as of December 31, 2018 related primarily to the exclusion of stock-based compensation expense from the Company’s cost sharing agreement, calculation of taxable E&P and related foreign tax credits, the ability to realize certain refund claims, and intercompany transactions. It is reasonably possible that unrecognized tax benefits will be decreased by $20.0 million within the next 12 months due to anticipated closure of audits, the expiration of certain statutes of limitation and closure of tax controversies.

Included in the balance of unrecognized tax benefits at December 31, 2018 are potential benefits of $86.2 million that if recognized would reduce the effective tax rate on income from continuing operations. Also included in the balance of unrecognized tax benefits as of December 31, 2018 are potential benefits of $4.1 million that, if recognized, would result in adjustments to other tax accounts, primarily deferred taxes.

The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding interest and penalties, for the years ended December 31 (in thousands):



	2018			2017
Beginning balance	$	60,269		$	37,099
Additions based on tax positions related to the current year	27,371			10,883
Additions for tax positions of prior years	14,691			24,299
Reductions for tax positions of prior years	(3,939		)	(10,613		)
Reductions for expiration of statutes	(6,293		)	(1,368		)
Settlements	(472		)	(1,769		)
Change in foreign currency exchange rates	(1,278		)	1,738
Ending balance	$	90,349		$	60,269

The Company accrues interest and penalties related to unrecognized tax benefits in its income tax provision. As of December 31, 2018 and 2017, the Company had $6.7 million and $6.4 million, respectively, of accrued interest and penalties related to unrecognized tax benefits. These amounts are in addition to the unrecognized tax benefits disclosed above. The total amount of interest and penalties recognized in the income tax provision for the years ended December 31, 2018 and 2017 was $0.7 million and $0.9 million, respectively.

The number of years with open statutes of limitation varies depending on the tax jurisdiction. The Company’s statutes are open with respect to the U.S. federal jurisdiction for 2014 and forward, and India for 2003 and forward. For other major taxing jurisdictions including U.S. states, the United Kingdom, Canada, Japan, France and Ireland, the Company's statutes vary and are open as far back as 2011.

Under U.S. GAAP, no provision for income taxes that may result from the remittance of earnings held overseas is required if the Company has the ability and intent to indefinitely reinvest such funds overseas. The Company continues to assert its intention to reinvest all accumulated undistributed foreign earnings in our non-U.S. operations, except in instances in which the repatriation of those earnings would result in minimal additional tax. Consequently, the Company has not recognized income tax expense that would result from the remittance of these earnings. The accumulated undistributed earnings of non-U.S. subsidiaries were approximately $171.0 million as of December 31, 2018. As a result of the Act, the income tax that would be payable if such earnings were not indefinitely invested is estimated at this time to be minimal.

Derivatives and Hedging

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

DERIVATIVES AND HEDGING

The Company enters into a limited number of derivative contracts to mitigate the cash flow risk associated with changes in interest rates on variable-rate debt and changes in foreign exchange rates on forecasted foreign currency transactions. The Company accounts for its outstanding derivative contracts in accordance with FASB ASC Topic 815, which requires all derivatives, including derivatives designated as accounting hedges, to be recorded on the balance sheet at fair value.

The following tables provide information regarding the Company’s outstanding derivatives contracts as of the dates indicated (in thousands, except for number of contracts):

December 31, 2018



Derivative Contract Type	Number of Contracts	Notional Amounts		Fair Value Asset (Liability), Net (3)			Balance Sheet Line Item	Unrealized Loss Recorded in AOCI/L
Interest rate swaps (1)	7	$	2,100,000	$	(10,681	)	Other liabilities	$	(7,770	)
Foreign currency forwards (2)	135	927,375		(1,942		)	Accrued liabilities	—
Total	142	$	3,027,375	$	(12,623	)		$	(7,770	)

December 31, 2017



Derivative Contract Type	Number of Contracts	Notional Amounts		Fair Value Asset (Liability), Net (3)		Balance Sheet Line Item	Unrealized Gain Recorded in AOCI/L
Interest rate swaps (1)	5	$	1,400,000	$	3,412	Other assets	$	2,483
Foreign currency forwards (2)	137	686,764		448		Other current assets	—
Total	142	$	2,086,764	$	3,860		$	2,483


(1)	The swaps have been designated and are accounted for as cash flow hedges of the forecasted interest payments on borrowings. As a result, changes in the fair value of the swaps are deferred and are recorded in AOCI/L, net of tax effect. Note 5 — Debt provides additional information.

(2)

The Company has foreign exchange transaction risk because it typically enters into transactions in the normal course of business that are denominated in foreign currencies that differ from the local functional currency. The Company enters into short-term foreign currency forward exchange contracts to mitigate the cash flow risk associated with changes in foreign currency rates on forecasted foreign currency transactions. These contracts are accounted for at fair value with realized and unrealized gains and losses recognized in Other income, net because the Company does not designate these contracts as hedges for accounting purposes. All of the outstanding foreign currency forward exchange contracts at December 31, 2018 matured by the end of January 2019.


(3)	See Note 12 — Fair Value Disclosures for the determination of the fair value of these instruments.

At December 31, 2018, all of the Company’s derivative counterparties were investment grade financial institutions. The Company did not have any collateral arrangements with its derivative counterparties and none of the derivative contracts contained credit-risk related contingent features.

The following table provides information regarding amounts recognized in the Consolidated Statements of Operations for derivative contracts for the years ended December 31 (in millions):



Amount recorded in:	2018			2017			2016
Interest (income) expense, net (1)	$	(1.9	)	$	7.9		$	7.6
Other expense (income), net (2)	10.4			(0.8		)	0.3
Total expense, net	$	8.5		$	7.1		$	7.9


(1)	Consists of interest (income) expense from interest rate swap contracts.


(2)	Consists of net realized and unrealized gains and losses on foreign currency forward contracts.

Fair Value Disclosures

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

FAIR VALUE DISCLOSURES

The Company’s financial instruments include cash equivalents, fees receivable from customers, accounts payable and accruals, all of which are normally short-term in nature. The Company believes that the carrying amounts of these financial instruments reasonably approximate their fair values due to their short-term nature. The Company’s financial instruments also include its outstanding variable-rate borrowings under the 2016 Credit Agreement. The Company believes that the carrying amounts of its variable-rate borrowings reasonably approximate their fair values because the rates of interest on those borrowings reflect current market rates of interest for similar instruments with comparable maturities.

The Company enters into a limited number of derivatives transactions but does not enter into repurchase agreements, securities lending transactions or master netting arrangements. Receivables or payables that result from derivatives transactions are recorded gross in the Company’s Consolidated Balance Sheets.

FASB ASC Topic 820 provides a framework for the measurement of fair value and a valuation hierarchy based on the transparency of inputs used in the valuation of assets and liabilities. Classification within the valuation hierarchy is based on the lowest level of input that is significant to the resulting fair value measurement. The valuation hierarchy contains three levels. Level 1 measurements consist of quoted prices in active markets for identical assets or liabilities. Level 2 measurements include significant other observable inputs such as quoted prices for similar assets or liabilities in active markets; identical assets or liabilities in inactive markets; observable inputs such as interest rates and yield curves; and other market-corroborated inputs. Level 3 measurements include significant unobservable inputs such as internally-created valuation models. The Company does not currently utilize Level 3 valuation inputs to remeasure any of its assets or liabilities. However, Level 3 inputs may be used by the Company in its required annual impairment review of recorded goodwill. Information regarding the periodic assessment of the Company’s goodwill is included in Note 1 — Business and Significant Accounting Policies. The Company does not typically transfer assets or liabilities between different levels of the valuation hierarchy.

The following table presents the fair value of certain financial assets and liabilities (in thousands):



Description:	December 31, 2018		December 31, 2017
Assets:
Values based on Level 1 inputs:
Deferred compensation plan assets (1)	$	8,956	$	29,108
Total Level 1 inputs	8,956		29,108
Values based on Level 2 inputs:
Deferred compensation plan assets (1)	57,690		59,017
Foreign currency forward contracts (2)	1,318		2,053
Interest rate swap contracts (3)	—		3,412
Total Level 2 inputs	59,008		64,482
Total Assets	$	67,964	$	93,590
Liabilities:
Values based on Level 2 inputs:
Deferred compensation plan liabilities (1)	$	68,570	$	89,900
Foreign currency forward contracts (2)	3,260		1,605
Interest rate swap contracts (3)	10,681		—
Senior Notes due 2025 (4)	776,160		837,560
Total Level 2 inputs	858,671		929,065
Total Liabilities	$	858,671	$	929,065

(1)

The Company has a deferred compensation plan for the benefit of certain highly compensated officers, managers and other key employees (see Note 13 — Employee Benefits). The assets consist of investments in money market funds, mutual funds and company-owned life insurance contracts. The money market funds consist of cash equivalents while the mutual fund investments consist of publicly-traded and quoted equity shares. The Company considers the fair value of these assets to be based on Level 1 inputs, and such assets had fair values of $9.0 million and $29.1 million as of December 31, 2018 and 2017, respectively. The carrying amounts of the life insurance contracts equal their cash surrender values. Cash surrender value represents the estimated amount that the Company would receive upon termination of a contract, which approximates fair value. The Company considers life insurance contracts to be valued based on Level 2 inputs, and such assets had fair values of $57.7 million and $59.0 million at December 31, 2018 and 2017, respectively. The related deferred compensation plan liabilities are recorded at fair value, or the estimated amount needed to settle the liability, which the Company considers to be a Level 2 input.


(2)	The Company enters into foreign currency forward exchange contracts to hedge the effects of adverse fluctuations in foreign currency exchange rates (see Note 11 — Derivatives and Hedging). Valuation of these contracts is based on observable foreign currency exchange rates in active markets, which the Company considers a Level 2 input.

(3)

The Company has interest rate swap contracts that hedge the risk of variability from interest payments on its borrowings (see Note 5 — Debt). The fair value of interest rate swaps is based on mark-to-market valuations prepared by a third-party broker. Those valuations are based on observable interest rates from recently executed market transactions and other observable market data, which the Company considers Level 2 inputs. The Company independently corroborates the reasonableness of the valuations prepared by the third-party broker through the use of an electronic quotation service.


(4)	As discussed in Note 5 — Debt, the Company has $800.0 million of principal amount fixed-rate Senior Notes due in 2025. The estimated fair value of the notes was derived from quoted market prices provided by an independent dealer, which the Company considers to be a Level 2 input.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Employee Benefits

12 Months Ended

Dec. 31, 2018

Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]

EMPLOYEE BENEFITS

Defined contribution plan. The Company has savings and investment plans (the “401k Plans”) covering substantially all U.S. employees. Company contributions are based on the level of employee contributions, up to a maximum of 4% of an employee’s eligible salary, subject to an annual maximum. For 2018, the maximum match was $7,200. Amounts expensed in connection with the 401k Plans totaled $36.7 million, $29.8 million and $22.9 million in 2018, 2017 and 2016, respectively.

Deferred compensation plan. The Company has supplemental deferred compensation plans for the benefit of certain highly compensated officers, managers and other key employees. The plans' investment assets are recorded in Other assets on the Consolidated Balance Sheets at fair value. The value of these assets was $66.6 million and $88.1 million at December 31, 2018 and 2017, respectively (see Note 12 — Fair Value Disclosures for fair value information). The corresponding deferred compensation plan liability, which was $68.6 million and $89.9 million at December 31, 2018 and 2017, respectively, is carried at fair value, and is adjusted with a corresponding charge or credit to compensation expense to reflect the fair value of the amount owed to the employees and is classified in Other liabilities on the Consolidated Balance Sheets. Compensation expense recognized for all deferred compensation plans was $1.7 million, $0.4 million and $0.1 million in 2018, 2017 and 2016, respectively.

Defined benefit pension plans. The Company has defined benefit pension plans in several of its international locations. Benefits paid under these plans are based on years of service and level of employee compensation. The Company's defined benefit pension plans are accounted for in accordance with FASB ASC Topics 715 and 960. The following are the components of defined benefit pension plan expense for the years ended December 31 (in thousands):



	2018			2017			2016
Service cost	$	3,145		$	2,820		$	2,780
Interest cost	840			765			850
Expected return on plan assets	(475		)	(360		)	(375		)
Recognition of actuarial loss	340			350			200
Total defined benefit pension plan expense	$	3,850		$	3,575		$	3,455

The following are the key assumptions used in the computation of pension expense for the years ended December 31:



	2018		2017		2016
Weighted average discount rate (1)	1.81	%	1.78	%	1.78	%
Average compensation increase	2.58	%	2.66	%	2.67	%


(1)	Discount rates are typically determined by utilizing the yields on long-term corporate or government bonds in the relevant country with a duration consistent with the expected term of the underlying pension obligations.

The following table provides information related to changes in the projected benefit obligation for the years ended December 31 (in thousands):



	2018			2017			2016
Projected benefit obligation at beginning of year	$	45,450		$	38,400		$	35,870
Service cost	3,145			2,820			2,780
Interest cost	840			765			850
Actuarial loss (gain) due to assumption changes and plan experience	(430		)	690			1,480
Additions and contractual termination benefits	(950		)	(860		)	—
Benefits paid (1)	(1,400		)	(920		)	(1,640		)
Foreign currency impact	(1,765		)	4,555			(940		)
Projected benefit obligation at end of year (2)	$	44,890		$	45,450		$	38,400


(1)	The Company projects the following benefit payments will be made in future years directly to plan participants: $1.2 million in 2019; $1.5 million in 2020; $1.6 million in 2021; $1.7 million in 2022; $2.1 million in 2023; and $12.1 million in total in the five years thereafter.


(2)	Measured as of December 31.

The following table provides information regarding the funded status of the plans and related amounts recorded in the Company’s Consolidated Balance Sheets as of December 31 (in thousands):



Funded status of the plans:	2018			2017			2016
Projected benefit obligation	$	44,890		$	45,450		$	38,400
Pension plan assets at fair value (1)	(19,460		)	(18,475		)	(14,465		)
Funded status – shortfall (2)	$	25,430		$	26,975		$	23,935



Amounts recorded in the Consolidated Balance Sheets for the plans:
Other liabilities — accrued pension obligation (2)	$	25,430		$	26,975		$	23,935
Stockholders’ equity — deferred actuarial loss (3)	$	(5,738	)	$	(5,861	)	$	(5,797	)

(1)

The pension plan assets are held by third-party trustees and are invested in a diversified portfolio of equities, high quality government and corporate bonds, and other investments. The assets are primarily valued based on Level 1 and Level 2 inputs under the fair value hierarchy in FASB ASC Topic 820, with the majority of the invested assets considered to be of low-to-medium investment risk. The Company projects a future long-term rate of return on these plan assets of 2.45%, which it believes is reasonable based on the composition of the assets and both current and projected market conditions. For the year ended December 31, 2018, the Company contributed $3.0 million to these plans, and benefits paid directly by the Company to participants were $1.4 million.


(2)	The Funded status - shortfall represents the amount of the projected benefit obligation that the Company has not funded with a third-party trustee. This amount is a liability of the Company and is recorded in Other liabilities on the Company’s Consolidated Balance Sheets.

(3)

The deferred actuarial loss as of December 31, 2018 is recorded in AOCI/L and will be reclassified out of AOCI/L and recognized as pension expense over approximately 13 years, subject to certain limitations set forth in FASB ASC Topic 715. The impact of this amortization on pension expense in 2019 is projected to result in approximately $0.2 million of additional expense. The amortization of deferred actuarial losses from AOCI/L to pension expense in each of the three years ended December 31, 2018 was immaterial.

The Company also maintains a reinsurance asset arrangement with a large international insurance company whose purpose is to provide funding for benefit payments for one of its plans. The reinsurance asset is not a pension plan asset but is an asset of the Company. At December 31, 2018 and 2017, the reinsurance asset was recorded at its cash surrender value of $9.0 million and $9.1 million, respectively, and classified in Other assets on the Company's Consolidated Balance Sheets. The Company believes that the cash surrender value approximates fair value and is equivalent to a Level 2 input under the FASB’s fair value hierarchy in FASB ASC Topic 820.

Segment Information

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

SEGMENT INFORMATION

Our products and services are currently delivered through three segments – Research, Conferences and Consulting, as follows:

•

Research provides trusted, objective insights and advice on the mission-critical priorities of leaders across all functional areas of the enterprise through research and other reports, briefings, proprietary tools, access to our analysts and advisors, peer networking services and membership programs that enable our clients to make better decisions. Gartner's traditional strengths in IT, marketing and supply chain research were enhanced in 2017 with Gartner's acquisition of CEB Inc., which added CEB's best practice and talent management research insights across a range of business functions, to include human resources, sales, legal and finance.

•

Conferences (formerly called Events) provides business professionals across the organization the opportunity to learn, share and network. From our flagship Chief Information Officer conference Gartner IT Symposium, to industry-leading conferences focused on specific business roles and topics, to member-driven sessions, our offerings enable attendees to experience the best of Gartner insight and advice live.


•	Consulting provides customized solutions to unique client needs through on-site, day-to-day support, as well as proprietary tools for measuring and improving IT performance with a focus on cost, performance, efficiency and quality.

The Company evaluates segment performance and allocates resources based on gross contribution margin. Gross contribution, as presented in the table below, is defined as operating income or loss excluding certain Cost of services and product development expenses, Selling, general and administrative expenses, Depreciation, Amortization of intangibles, and Acquisition and integration charges. Certain bonus and fringe benefit costs included in consolidated Cost of services and product development are not allocated to segment expense. The accounting policies used by the reportable segments are the same as those used by the Company. There are no intersegment revenues. The Company does not identify or allocate assets, including capital expenditures, by reportable segment. Accordingly, assets are not reported by segment because the information is not available by segment and is not reviewed in the evaluation of segment performance or in making decisions in the allocation of resources.

The Company earns revenue from clients in many countries. Other than the United States, there is no individual country in which revenues from external clients represent 10% or more of the Company’s consolidated revenues. Additionally, no single client accounted for 10% or more of total revenue and the loss of a single client, in management’s opinion, would not have a material adverse effect on revenues.

The following tables present information about the Company’s reportable segments for the periods indicated (in thousands):



	Research		Conferences		Consulting		Other		Consolidated
2018
Revenues	$	3,105,764	$	410,461	$	353,667	$	105,562	$	3,975,454
Gross contribution	2,144,097		207,260		102,541		65,075		2,518,973
Corporate and other expenses									(2,259,258		)
Operating income									$	259,715

	Research		Conferences		Consulting		Other		Consolidated
2017
Revenues	$	2,471,280	$	337,903	$	327,661	$	174,650	$	3,311,494
Gross contribution	1,653,014		163,480		93,643		90,249		2,000,386
Corporate and other expenses									(2,006,715		)
Operating loss									$	(6,329	)

	Research		Conferences		Consulting		Other		Consolidated
2016
Revenues	$	1,857,001	$	268,605	$	318,934	$	—	$	2,444,540
Gross contribution	1,285,611		136,655		89,734		—		1,512,000
Corporate and other expenses									(1,206,859		)
Operating income									$	305,141

The following table provides a reconciliation of total segment gross contribution to net income for the years ended December 31 (in thousands):



	2018		2017			2016
Total segment gross contribution	$	2,518,973	$	2,000,386		$	1,512,000
Costs and expenses:
Cost of services and product development - unallocated (1)	12,319		9,090			13,108
Selling, general and administrative	1,884,141		1,599,004			1,089,184
Depreciation and amortization	255,601		240,171			61,969
Acquisition and integration charges	107,197		158,450			42,598
Operating income (loss)	259,715		(6,329		)	305,141
Interest expense and other, net	124,041		121,488			16,710
Gain from divested operations	45,447		—			—
Provision (benefit) for income taxes	58,665		(131,096		)	94,849
Net income	$	122,456	$	3,279		$	193,582


(1)	The unallocated amounts consist of certain bonus and related fringe costs recorded in consolidated Cost of services and product development expense that are not allocated to segment expense. The Company's policy is to only allocate bonus and related fringe charges to segments for up to 100% of the segment employee's target bonus. Amounts above 100% are absorbed by corporate.

Disaggregated revenue information by reportable segment for the three years ended December 31, 2018, including our Other segment, is presented in Note 1 – Business and Significant Accounting Policies. Long-lived asset information by geographic location as of December 31 is summarized in the table below (in thousands).



	2018		2017		2016
Long-lived assets: (1)
United States and Canada	$	305,928	$	288,735	$	143,921
Europe, Middle East and Africa	67,306		84,840		42,326
Other International	50,800		41,674		24,630
Total long-lived assets	$	424,034	$	415,249	$	210,877


(1)	Excludes goodwill, intangible assets and held-for-sale assets.

Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2018

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

VALUATION AND QUALIFYING ACCOUNTS

The Company maintains an allowance for losses that is comprised of a bad debt allowance and, through December 31, 2017, a revenue reserve. Provisions are charged against earnings either as an increase to expense or, prior to 2018, a reduction in revenues.

The following table summarizes activity in the Company’s allowance for losses for the years ended December 31 (in thousands):



	Balance at Beginning of Year		Additions Charged to Expense		Additions Charged Against Revenues		Deductions from Reserve			Reclassification to Accounts Payable and Accrued Liabilities			Balance at End of Year
2018:
Bad debt allowance (1)	$	12,700	$	12,500	$	—	$	(11,300	)	$	(6,200	)	$	7,700
2017:
Bad debt allowance and revenue reserve (1)	$	7,400	$	16,600	$	5,500	$	(16,800	)	$	—		$	12,700
2016:
Bad debt allowance and revenue reserve	$	6,900	$	4,750	$	4,850	$	(9,100	)	$	—		$	7,400

(1) The allowance for losses at December 31, 2017 included $6.2 million that was attributable to the Company's revenue reserve. As a result of the Company's adoption of ASU No. 2014-09 on January 1, 2018, the revenue reserve balance is now included in Accounts payable and accrued liabilities on the Company's Consolidated Balance Sheet. Note 1 — Business and Significant Accounting Policies provides additional information regarding the Company's adoption of ASU No. 2014-09.

Business and Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of presentation

The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”), as defined in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 270 for financial information and with the applicable instructions of U.S. Securities and Exchange Commission (“SEC”) Regulation S-X. The fiscal year of Gartner is the twelve-month period from January 1 through December 31. All references to 2018, 2017 and 2016 herein refer to the fiscal year unless otherwise indicated.

Principles of consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances have been eliminated.

Use of estimates

The preparation of the accompanying consolidated financial statements requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Such estimates include the valuation of fees receivable, goodwill, intangible assets and other long-lived assets, as well as tax accruals and other liabilities. In addition, estimates are used in revenue recognition, income tax expense or benefit, performance-based compensation charges, depreciation and amortization. Management believes its use of estimates in the accompanying consolidated financial statements to be reasonable.

Business acquisitions

The Company had business acquisitions in both 2017 and 2016 and information related to those acquisitions is included in Note 2 – Acquisitions and Divestitures. The Company accounts for business acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic 805, Business Combinations. The acquisition method of accounting requires the Company to record the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, with any excess of the consideration transferred over the estimated fair value of the net assets acquired, including identifiable intangible assets, to be recorded to goodwill. Under the acquisition method, the operating results of acquired companies are included in the Company's consolidated financial statements beginning on the date of acquisition.

Revenue recognition

On January 1, 2018, the Company adopted Accounting Standards Update ("ASU") No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments required changes in our revenue recognition policies as well as enhanced disclosures. The Company adopted ASU No. 2014-09 using the modified retrospective method of adoption. Under this method of adoption, the cumulative effect of applying the new standard is recorded at the date of initial application, with no restatement of the comparative prior periods presented. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. Prior to January 1, 2018, the Company recognized revenue in accordance with then-existing U.S. GAAP and SEC Staff Accounting Bulletin No. 104, "Revenue Recognition" (“prior GAAP”). Under both ASU No. 2014-09 and prior GAAP, revenue can only be recognized when all of the required criteria are met. Information regarding our adoption of ASU No. 2014-09 and its impact on the Company's consolidated financial statements and related disclosures is provided below under the heading "Adoption of new accounting standards."

Allowance for losses and the revenue reserve

Because the adoption of ASU No. 2014-09 on January 1, 2018 discussed above affected the allowance for losses, information regarding the allowance is provided below under the heading "Adoption of new accounting standards."

Cost of services and product development

COS expense includes the direct costs incurred in the creation and delivery of our products and services. These costs primarily relate to personnel.

Selling, general and administrative

SG&A expense includes direct and indirect selling costs, general and administrative costs, and charges against earnings related to uncollectible accounts.

Commissions expense

The Company records deferred commissions upon the signing of customer contracts and amortizes the deferred amount as commission expense over a period that considers various relevant factors. Commission expense is included in SG&A expense in the Consolidated Statements of Operations. Additional information regarding deferred commissions and the amortization of such costs is provided below under the heading "Adoption of new accounting standards."

Stock-based compensation expense

The Company accounts for stock-based compensation awards in accordance with FASB ASC Topics 505 and 718 and SEC Staff Accounting Bulletins No. 107 and No. 110. Stock-based compensation expense for equity awards is based on the fair value of the award on the date of grant. The Company recognizes stock-based compensation expense over the period that the related service is performed, which is generally the same as the vesting period of the underlying award. During 2018, 2017 and 2016, the Company recognized $66.2 million, $78.9 million and $46.7 million, respectively, of stock-based compensation expense.

Income taxes

The Company uses the asset and liability method of accounting for income taxes. We estimate our income taxes in each of the jurisdictions where we operate. This process involves estimating our current tax expense or benefit together with assessing temporary differences resulting from differing treatment of items for tax and accounting purposes. These differences result in deferred tax assets and liabilities, which are included in our consolidated balance sheets. When assessing the realizability of deferred tax assets, we consider if it is more likely than not that some or all of the deferred tax assets will not be realized. In making this assessment, we consider the availability of loss carryforwards, projected reversals of deferred tax liabilities, projected future taxable income, and ongoing prudent and feasible tax planning strategies. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained based on the technical merits of the position.

Cash and cash equivalents

Includes cash and all highly liquid investments with original maturities of three months or less, which are considered cash equivalents. The carrying value of cash equivalents approximates fair value due to their short-term maturity. Investments with maturities of more than three months are classified as marketable securities. Interest earned is classified in Interest income in the Consolidated Statements of Operations.

Property, equipment and leasehold improvements

The Company leases all of its facilities and certain equipment. These leases are all classified as operating leases in accordance with FASB ASC Topic 840, Leases. The cost of these operating leases, including any contractual rent increases, rent concessions and landlord incentives, is recognized ratably over the life of the related lease agreement. Lease expense was $93.5 million, $87.9 million and $38.0 million in 2018, 2017 and 2016, respectively.

Finite-Lived Intangible assets

The Company has finite-lived intangible assets that are amortized against earnings using the straight-line method over the expected useful life of the underlying asset.

Goodwill

Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair values of the tangible and identifiable intangible net assets acquired. Evaluations of the recoverability of goodwill are performed in accordance with FASB ASC Topic 350, which requires an annual assessment of potential goodwill impairment at the reporting unit level and whenever events or changes in circumstances indicate that the carrying value of goodwill may not be recoverable. The annual assessment of the recoverability of recorded goodwill can be based on either a qualitative or quantitative assessment or a combination of the two approaches. Both methods utilize estimates which, in turn, require judgments and assumptions regarding future trends and events. As a result, both the precision and reliability of the resulting estimates are subject to uncertainty. If our annual goodwill impairment evaluation determines that the fair value of a reporting unit is less than its related carrying amount, we may recognize an impairment charge. In connection with our most recent annual impairment test of goodwill during the quarter ended September 30, 2018, which indicated no impairment of recorded goodwill, the Company utilized the quantitative approach in assessing the fair values of its reporting units relative to their respective carrying values.

Impairment of long-lived assets

The Company's long-lived assets primarily consist of intangible assets other than goodwill and property, equipment and leasehold improvements. The Company reviews its long-lived asset groups for impairment whenever events or changes in circumstances indicate that the carrying amount of the respective asset may not be recoverable. Such evaluation may be based on a number of factors, including current and projected operating results and cash flows, and changes in management’s strategic direction as well as external economic and market factors. The Company evaluates the recoverability of these assets by determining whether their carrying values can be recovered through undiscounted future operating cash flows. If events or circumstances indicate that the carrying values might not be recoverable based on undiscounted future operating cash flows, an impairment loss would be recognized. The amount of impairment, if any, is measured based on the difference between the projected discounted future operating cash flows, using a discount rate reflecting the Company’s average cost of funds, and the carrying value of the asset. The Company did not record any impairment charges for long-lived asset groups during the three-year period ended December 31, 2018.

Pension obligations

The Company has defined benefit pension plans in several of its international locations (see Note 13 — Employee Benefits). Benefits earned under these plans are generally based on years of service and level of employee compensation. The Company accounts for its defined benefit plans in accordance with the requirements of FASB ASC Topic 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations. The Company recognized $3.9 million, $3.6 million and $3.5 million of pension expense in 2018, 2017 and 2016, respectively.

Debt

The Company presents amounts borrowed in the Consolidated Balance Sheets at amortized cost, net of deferred financing fees. Interest accrued on amounts borrowed is classified as Interest expense in the Consolidated Statements of Operations. The Company had $2.3 billion of principal amount of debt outstanding at December 31, 2018 compared to $3.3 billion at December 31, 2017, which reflects the Company's significant principal repayments on its debt subsequent to the completion of the CEB Inc. acquisition. Note 5 — Debt provides information regarding the Company's debt.

Foreign currency exposure

The functional currency of our foreign subsidiaries is typically the local currency. All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense items are translated at average exchange rates for the year. The resulting translation adjustments are recorded as foreign currency translation adjustments, a component of Accumulated other comprehensive (loss) income, net within the Stockholders’ Equity section of the Consolidated Balance Sheets.

Comprehensive income

The Company reports comprehensive income in a separate statement called the Consolidated Statements of Comprehensive Income, which is included herein. The Company's comprehensive income disclosures are included in Note 7 — Stockholders' Equity.

Fair value disclosures

The Company has a limited number of assets and liabilities that are adjusted to fair value at each balance sheet date. The Company’s fair value disclosures are included in Note 12 — Fair Value Disclosures.

Concentrations of credit risk

Assets that may subject the Company to concentration of credit risk consist primarily of short-term, highly liquid investments classified as cash equivalents, fees receivable, contract assets, interest rate swaps and a pension reinsurance asset. The majority of the Company’s cash equivalent investments and its interest rate swap contracts are with investment grade commercial banks. Fees receivable and contract asset balances deemed to be collectible from customers have limited concentration of credit risk due to our diverse customer base and geographic dispersion. The Company’s pension reinsurance asset (see Note 13 — Employee Benefits) is maintained with a large international insurance company that was rated investment grade as of December 31, 2018 and 2017.

Stock repurchase programs

The Company records the cost to repurchase its own common shares as treasury stock. During 2018, 2017 and 2016, the Company used $260.8 million, $41.3 million and $59.0 million, respectively, in cash for stock repurchases (see Note 7 — Stockholders’ Equity for additional information). Shares repurchased by the Company are added to treasury shares and are not retired.

Adoption of new accounting standards

The Company adopted the accounting standards described below during 2018:



	December 31,
	2018		2017		2016		2015
Cash and cash equivalents	$	156,368	$	538,908	$	474,233	$	372,976
Restricted cash classified in (1), (2):
Prepaid expenses and other current assets	2,295		15,148		25,121		13,505
Other assets	—		3,002		—		25,626
Cash classified as held-for-sale (3)	—		10,000		—		—
Cash and cash equivalents and restricted cash per the Consolidated Statements of Cash Flows	$	158,663	$	567,058	$	499,354	$	412,107

(1)


(2)	Restricted cash is recorded in Prepaid expenses and other current assets and Other assets in the Company's consolidated balance sheets with the short-term or long-term classification dependent on the projected timing of disbursements to the sellers.


(3)	Represents cash classified as a held-for-sale asset for the CEB Talent Assessment business that was acquired as part of the CEB Inc. acquisition. See Note 2 — Acquisitions and Divestitures for additional information.

The following sections provide an overview of the Company's revenues by segment along with the required disclosures under the new revenue recognition standard.

Our business and our revenues

Gartner currently delivers its products and services globally through three business segments: Research, Conferences and Consulting. Our revenues from those business segments are discussed below.

Research

Conferences

Consulting

Overview of ASU No. 2014-09

ASU No. 2014-09 requires a five-step evaluative process that consists of:


(1)	Identifying the contract with the customer;


(2)	Identifying the performance obligations in the contract;


(3)	Determining the transaction price for the contract;


(4)	Allocating the transaction price to the performance obligations in the contract; and


(5)	Recognizing revenue when (or as) performance obligations are satisfied.

Required Disclosures under ASU No. 2014-09

Disaggregated Revenues

Year Ended December 31, 2018



	Research		Conferences		Consulting		Other (1)		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,994,016	$	256,219	$	205,874	$	58,843	$	2,514,952
Europe, Middle East and Africa	737,129		105,909		119,258		38,194		1,000,490
Other International	374,619		48,333		28,535		8,525		460,012
Total revenues	$	3,105,764	$	410,461	$	353,667	$	105,562	$	3,975,454

Year Ended December 31, 2017



	Research		Conferences		Consulting		Other (1)		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,600,847	$	210,698	$	188,022	$	92,799	$	2,092,366
Europe, Middle East and Africa	597,943		86,567		111,792		59,119		855,421
Other International	272,490		40,638		27,847		22,732		363,707
Total revenues	$	2,471,280	$	337,903	$	327,661	$	174,650	$	3,311,494

Year Ended December 31, 2016



	Research		Conferences		Consulting		Other		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,178,575	$	162,162	$	179,011	$	—	$	1,519,748
Europe, Middle East and Africa	434,753		72,926		109,042		—		616,721
Other International	243,673		33,517		30,881		—		308,071
Total revenues	$	1,857,001	$	268,605	$	318,934	$	—	$	2,444,540


(1)	The decline in Other segment revenues in 2018 compared to 2017 was due to divestitures. Information regarding the divestitures is included in Note 2 – Acquisitions and Divestitures.


(2)	Revenues are reported based on where the sale is fulfilled.

Year Ended December 31, 2018



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	2,851,176	$	—	$	294,397	$	86,667	$	3,232,240
Transferred at a point in time (2)	254,588		410,461		59,270		18,895		743,214
Total revenues	$	3,105,764	$	410,461	$	353,667	$	105,562	$	3,975,454

Year Ended December 31, 2017



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	2,275,377	$	—	$	269,720	$	141,331	$	2,686,428
Transferred at a point in time (2)	195,903		337,903		57,941		33,319		625,066
Total revenues	$	2,471,280	$	337,903	$	327,661	$	174,650	$	3,311,494

Year Ended December 31, 2016



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	1,710,786	$	—	$	267,809	$	—	$	1,978,595
Transferred at a point in time (2)	146,215		268,605		51,125		—		465,945
Total revenues	$	1,857,001	$	268,605	$	318,934	$	—	$	2,444,540

(1)


(2)	The revenues in this category were recognized in connection with performance obligations that were satisfied at the point in time the contractual deliverables were provided to the customer.

Customer Contract Assets and Liabilities

The table below provides information regarding certain of the Company’s balance sheet accounts that pertain to its contracts with customers, excluding held-for-sale businesses (in thousands):



	December 31,
	2018		2017
Assets:
Fees receivable, gross (1)	$	1,262,818	$	1,162,871

Contract assets (2)	$	26,119	$	26,672

Contract liabilities:
Deferred revenues (current liability) (3)	$	1,745,244	$	1,630,198
Non-current deferred revenues (3)	21,194		16,205
Total contract liabilities	$	1,766,438	$	1,646,403


(1)	Fees receivable represent the unconditional right of payment from our customers and include both billed and unbilled amounts.

(2)


(3)	Deferred revenues represent amounts (i) for which the Company has received an upfront customer payment or (ii) that pertain to recognized fees receivable. Both situations occur before the completion of our performance obligation(s).

Allowance for Losses and the Revenue Reserve

Costs of obtaining and fulfilling a customer contract

Accounting standards effective in 2019

Accounting standards effective in 2020

Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Property, Plant and Equipment

The Company's total fixed assets, less accumulated depreciation and amortization, consisted of the following (in thousands):



	Useful Life	December 31,
Category	(Years)	2018			2017
Computer equipment and software	2-7	$	210,955		$	189,015
Furniture and equipment	3-8	85,002			67,288
Leasehold improvements	2-15	218,405			175,716
		514,362			432,019
Less — accumulated depreciation and amortization		(246,697		)	(210,512		)
Property, equipment and leasehold improvements, net		$	267,665		$	221,507

Schedule of Changes in Intangible Assets Subject to Amortization

Changes in intangible assets subject to amortization during the two-year period ended December 31, 2018 were as follows (in thousands):



December 31, 2018	Customer Relationships			Software			Content			Other			Total
Gross cost at December 31, 2017 (1)	$	1,200,316		$	123,424		$	104,313		$	54,929		$	1,482,982
Divestitures (2)	(45,175		)	(321		)	(473		)	(160		)	(46,129		)
Write-off of fully amortized intangible assets	(303		)	(11,715		)	(669		)	(3,311		)	(15,998		)
Foreign currency translation impact and other (3)	(23,182		)	(687		)	(4,329		)	204			(27,994		)
Gross cost	1,131,656			110,701			98,842			51,662			1,392,861
Accumulated amortization (4)	(184,918		)	(38,901		)	(92,717		)	(33,760		)	(350,296		)
Balance at December 31, 2018	$	946,738		$	71,800		$	6,125		$	17,902		$	1,042,565



December 31, 2017	Customer Relationships			Software			Content			Other			Total
Gross cost at December 31, 2016	$	63,369		$	16,025		$	3,728		$	33,645		$	116,767
Additions due to acquisitions (5)	1,253,312			180,787			141,707			24,384			1,600,190
Write-off of fully amortized intangible assets	—			—			(4,227		)	—			(4,227		)
Reclassified as held-for-sale (6)	(140,156		)	(69,012		)	(38,593		)	(2,711		)	(250,472		)
Foreign currency translation impact	23,791			(4,376		)	1,698			(389		)	20,724
Gross cost (1)	1,200,316			123,424			104,313			54,929			1,482,982
Accumulated amortization (4)	(92,983		)	(26,344		)	(47,475		)	(24,158		)	(190,960		)
Balance at December 31, 2017 (1)	$	1,107,333		$	97,080		$	56,838		$	30,771		$	1,292,022


(1)	Excludes certain amounts related to held-for-sale operations.


(2)	Represents amounts related to divested businesses. See Note 2 — Acquisitions and Divestitures for additional information.


(3)	Includes the foreign currency translation impact and certain other adjustments.


(4)	Finite-lived intangible assets are amortized using the straight-line method over the following periods: Customer relationships—4 to 13 years; Software—3 to 7 years; Content—1.5 to 5 years; and Other —2 to 5 years.


(5)	The additions were primarily due to the Company's acquisitions of CEB Inc. and L2, Inc. during April 2017 and March 2017, respectively. See Note 2 — Acquisitions and Divestitures for additional information.


(6)	Represents amounts reclassified (net) as held-for-sale assets related to the CEB Talent Assessment business. See Note 2 — Acquisitions and Divestitures for additional information.

Schedule of Estimated Future Amortization Expense by Year From Amortizable Intangibles

The estimated future amortization expense by year for finite-lived intangible assets is as follows (in thousands):



2019	$	129,394
2020	122,756
2021	102,338
2022	92,801
2023 and thereafter	595,276
	$	1,042,565

Schedule of Changes to The Carrying Amount of Goodwill by Reporting Unit

The following table presents changes to the carrying amount of goodwill by segment, including the Company's Other segment, during the two-year period ended December 31, 2018 (in thousands):



	Research			Conferences			Consulting			Other			Total
Balance at December 31, 2016 (1)	$	595,450		$	46,523		$	96,480		$	—		$	738,453
Additions due to acquisitions (2)	2,042,514			140,914			—			274,363			2,457,791
Reclassified as held-for-sale (3)	—			—			—			(212,994		)	(212,994		)
Foreign currency translation impact	(18,287		)	483			1,318			20,530			4,044
Balance at December 31, 2017	2,619,677			187,920			97,798			81,899			2,987,294
Divestitures (4)	(2,500		)	—			—			(90,078		)	(92,578		)
Foreign currency translation impact and other (5)	21,241			(266		)	(734		)	8,179			28,420
Balance at December 31, 2018	$	2,638,418		$	187,654		$	97,064		$	—		$	2,923,136


(1)	The Company does not have any accumulated goodwill impairment losses.


(2)	The 2017 goodwill additions are due to the acquisitions of CEB Inc. and L2, Inc. during April 2017 and March 2017, respectively. See Note 2 – Acquisitions and Divestitures for additional information.


(3)	Represents amounts reclassified as held-for-sale assets related to the CEB Talent Assessment business. See Note 2 – Acquisitions and Divestitures for additional information.


(4)	Represents amounts related to divested businesses. See Note 2 – Acquisitions and Divestitures for additional information.


(5)	Includes the foreign currency translation impact and certain measurement period adjustments related to the acquisition of CEB Inc.

Schedule of Cash and Cash Equivalents



	December 31,
	2018		2017		2016		2015
Cash and cash equivalents	$	156,368	$	538,908	$	474,233	$	372,976
Restricted cash classified in (1), (2):
Prepaid expenses and other current assets	2,295		15,148		25,121		13,505
Other assets	—		3,002		—		25,626
Cash classified as held-for-sale (3)	—		10,000		—		—
Cash and cash equivalents and restricted cash per the Consolidated Statements of Cash Flows	$	158,663	$	567,058	$	499,354	$	412,107

(1)


(2)	Restricted cash is recorded in Prepaid expenses and other current assets and Other assets in the Company's consolidated balance sheets with the short-term or long-term classification dependent on the projected timing of disbursements to the sellers.


(3)	Represents cash classified as a held-for-sale asset for the CEB Talent Assessment business that was acquired as part of the CEB Inc. acquisition. See Note 2 — Acquisitions and Divestitures for additional information.

Schedule of Restricted Cash



	December 31,
	2018		2017		2016		2015
Cash and cash equivalents	$	156,368	$	538,908	$	474,233	$	372,976
Restricted cash classified in (1), (2):
Prepaid expenses and other current assets	2,295		15,148		25,121		13,505
Other assets	—		3,002		—		25,626
Cash classified as held-for-sale (3)	—		10,000		—		—
Cash and cash equivalents and restricted cash per the Consolidated Statements of Cash Flows	$	158,663	$	567,058	$	499,354	$	412,107

(1)


(2)	Restricted cash is recorded in Prepaid expenses and other current assets and Other assets in the Company's consolidated balance sheets with the short-term or long-term classification dependent on the projected timing of disbursements to the sellers.


(3)	Represents cash classified as a held-for-sale asset for the CEB Talent Assessment business that was acquired as part of the CEB Inc. acquisition. See Note 2 — Acquisitions and Divestitures for additional information.

Schedule of Disaggregation of Revenue by Reportable Segment

Our disaggregated revenue information by reportable segment, including our Other segment, is presented for the years indicated in the tables below (in thousands).

Year Ended December 31, 2018



	Research		Conferences		Consulting		Other (1)		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,994,016	$	256,219	$	205,874	$	58,843	$	2,514,952
Europe, Middle East and Africa	737,129		105,909		119,258		38,194		1,000,490
Other International	374,619		48,333		28,535		8,525		460,012
Total revenues	$	3,105,764	$	410,461	$	353,667	$	105,562	$	3,975,454

Year Ended December 31, 2017



	Research		Conferences		Consulting		Other (1)		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,600,847	$	210,698	$	188,022	$	92,799	$	2,092,366
Europe, Middle East and Africa	597,943		86,567		111,792		59,119		855,421
Other International	272,490		40,638		27,847		22,732		363,707
Total revenues	$	2,471,280	$	337,903	$	327,661	$	174,650	$	3,311,494

Year Ended December 31, 2016



	Research		Conferences		Consulting		Other		Total
Primary Geographic Markets: (2)
United States and Canada	$	1,178,575	$	162,162	$	179,011	$	—	$	1,519,748
Europe, Middle East and Africa	434,753		72,926		109,042		—		616,721
Other International	243,673		33,517		30,881		—		308,071
Total revenues	$	1,857,001	$	268,605	$	318,934	$	—	$	2,444,540


(1)	The decline in Other segment revenues in 2018 compared to 2017 was due to divestitures. Information regarding the divestitures is included in Note 2 – Acquisitions and Divestitures.


(2)	Revenues are reported based on where the sale is fulfilled.

Schedule of Disaggregation of Revenue

Year Ended December 31, 2018



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	2,851,176	$	—	$	294,397	$	86,667	$	3,232,240
Transferred at a point in time (2)	254,588		410,461		59,270		18,895		743,214
Total revenues	$	3,105,764	$	410,461	$	353,667	$	105,562	$	3,975,454

Year Ended December 31, 2017



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	2,275,377	$	—	$	269,720	$	141,331	$	2,686,428
Transferred at a point in time (2)	195,903		337,903		57,941		33,319		625,066
Total revenues	$	2,471,280	$	337,903	$	327,661	$	174,650	$	3,311,494

Year Ended December 31, 2016



	Research		Conferences		Consulting		Other		Total
Timing of Revenue Recognition:
Transferred over time (1)	$	1,710,786	$	—	$	267,809	$	—	$	1,978,595
Transferred at a point in time (2)	146,215		268,605		51,125		—		465,945
Total revenues	$	1,857,001	$	268,605	$	318,934	$	—	$	2,444,540

(1)


(2)	The revenues in this category were recognized in connection with performance obligations that were satisfied at the point in time the contractual deliverables were provided to the customer.

Schedule for Contract with Customer, Asset and Liability

The table below provides information regarding certain of the Company’s balance sheet accounts that pertain to its contracts with customers, excluding held-for-sale businesses (in thousands):



	December 31,
	2018		2017
Assets:
Fees receivable, gross (1)	$	1,262,818	$	1,162,871

Contract assets (2)	$	26,119	$	26,672

Contract liabilities:
Deferred revenues (current liability) (3)	$	1,745,244	$	1,630,198
Non-current deferred revenues (3)	21,194		16,205
Total contract liabilities	$	1,766,438	$	1,646,403


(1)	Fees receivable represent the unconditional right of payment from our customers and include both billed and unbilled amounts.

(2)


(3)	Deferred revenues represent amounts (i) for which the Company has received an upfront customer payment or (ii) that pertain to recognized fees receivable. Both situations occur before the completion of our performance obligation(s).

Acquisitions and Divestiture (Tables)

12 Months Ended

Dec. 31, 2018

Mergers, Acquisitions And Dispositions Disclosures [Abstract]

Summary of amounts related to new building



	2018			2017
Liability balance at beginning of the period	$	12,961		$	—
Charges and adjustments, net (1)	69,790			13,087
Payments, net of $2,515 in sublease rent during 2018	(26,087		)	(126		)
Liability balance at end of the period (2)	$	56,664		$	12,961


(1)	During 2018, the Company recognized $7.5 million of expense for changes in the original estimates of its exit cost obligations. The corresponding amount for 2017 was a benefit of $10.1 million.


(2)	In total, we estimate that the Company will make net cash payments of approximately $90.6 million for exit costs in connection with the activities described herein. Through December 31, 2018, in the aggregate, we have expensed $82.9 million and had net cash outlays of $26.2 million related to such activities.

Schedule of aggregate purchase price for acquisitions

The following table summarizes the aggregate consideration paid for these acquisitions during 2017 (in thousands):



Aggregate consideration (1):	CEB		L2		Total
Cash paid at close (2), (3)	$	2,687,704	$	134,199	$	2,821,903
Additional cash paid (2)	12,465		—		12,465
Fair value of Gartner equity (4)	818,660		—		818,660
Total	$	3,518,829	$	134,199	$	3,653,028


(1)	Includes the total consideration transferred for 100% of the outstanding capital stock of the acquired businesses.


(2)	The cash paid at close represents the gross contractual amount paid. The Company paid the additional $12.5 million in cash in third quarter 2017. Net of cash acquired and for cash flow reporting purposes, the Company paid a total of approximately $2.64 billion in cash for acquisitions in 2017.


(3)	The Company borrowed a total of approximately $2.8 billion in conjunction with the CEB acquisition (see Note 5 — Debt for additional information).


(4)	Consists of the fair value of (i) Gartner common stock issued (see Note 7 — Stockholders' Equity for additional information) and (ii) stock-based compensation replacement awards.

Summary of the allocation of the purchase price to the fair value of the assets and liabilities assumed

The following table summarizes the allocation of the purchase price to the fair value of the assets acquired and liabilities assumed for the acquisitions of L2 and CEB (in thousands):



	CEB (3)		L2 (4)		Total
Assets:
Cash	$	194,706	$	4,852	$	199,558
Fees receivable	175,440		8,277		183,717
Prepaid expenses and other current assets	53,610		1,167		54,777
Property, equipment and leasehold improvements	51,399		663		52,062
Goodwill (1)	2,349,589		108,202		2,457,791
Finite-lived intangible assets (2)	1,584,300		15,890		1,600,190
Other assets	66,818		13,067		79,885
Total assets	4,475,862		152,118		4,627,980
Liabilities:
Accounts payable and accrued liabilities	142,134		3,050		145,184
Deferred revenues (current)	246,472		13,200		259,672
Other liabilities	568,427		1,669		570,096
Total liabilities	957,033		17,919		974,952
Net assets acquired	$	3,518,829	$	134,199	$	3,653,028

(1)

(2)

(3)



	Twelve Months Ended
	December 31,
	2017		2016
Pro forma total revenue	$	3,726,470	$	3,183,070
Pro forma net income (loss)	150,167		(241,423		)
Pro forma basic and diluted income (loss) per share	$	1.66	$	(2.68	)

The pro forma results have been prepared in accordance with U.S. GAAP and include the following pro forma adjustments:

(b) A change in revenue as a result of the required fair value adjustment to deferred revenue.

(4)

Schedule of pro forma financial information

Had the Company acquired CEB in prior periods, the impact to the Company's operating results would have been material, and as a result the following pro forma consolidated financial information is presented as if CEB had been acquired by the Company on January 1, 2016 (in thousands, except per share amounts):



	Twelve Months Ended
	December 31,
	2017		2016
Pro forma total revenue	$	3,726,470	$	3,183,070
Pro forma net income (loss)	150,167		(241,423		)
Pro forma basic and diluted income (loss) per share	$	1.66	$	(2.68	)

Other Assets (Tables)

12 Months Ended

Dec. 31, 2018

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Schedule of Other Assets

Other assets consist of the following (in thousands):



	December 31,
	2018		2017
Benefit plan-related assets	$	75,653	$	97,525
Non-current deferred tax assets	34,494		31,067
Other	46,222		65,150
Total other assets	$	156,369	$	193,742

Accounts Payable, Accrued, and Other Liabilities (Tables)

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

Schedule of Accounts Payable and Accrued Liabilities

Accounts payable and accrued liabilities consist of the following (in thousands):



	December 31,
	2018		2017
Accounts payable	$	37,508	$	49,000
Payroll and employee benefits payable	143,803		120,278
Severance and retention bonus payable	28,292		44,685
Bonus payable	170,719		162,710
Commissions payable	126,844		108,969
Taxes payable	19,725		46,758
Other accrued liabilities	183,222		134,421
Total accounts payable and accrued liabilities	$	710,113	$	666,821

Schedule of Other Liabilities

Other liabilities consist of the following (in thousands):



	December 31,
	2018		2017
Non-current deferred revenue	$	21,194	$	16,205
Long-term taxes payable	66,304		66,386
Benefit plan-related liabilities	96,033		118,868
Lease-related matters	165,374		115,840
Non-current deferred tax liabilities	214,687		206,338
Other	50,081		54,362
Total other liabilities	$	613,673	$	577,999

Debt (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of Debt

The following table summarizes the Company’s total outstanding borrowings (in thousands):



	December 31,
Description:	2018			2017
2016 Credit Agreement - Term loan A facility (1)	$	1,355,062		$	1,429,312
2016 Credit Agreement - Term loan B facility (2)	—			496,250
2016 Credit Agreement - Revolving credit facility (1), (3)	155,000			595,000
Senior notes (4)	800,000			800,000
Other (5)	2,030			2,500
Principal amount outstanding (6), (7)	2,312,092			3,323,062
Less: deferred financing fees (8)	(30,405		)	(44,217		)
Net balance sheet carrying amount	$	2,281,687		$	3,278,845


(1)	The contractual annualized interest rate as of December 31, 2018 on the Term loan A facility and the revolving credit facility was 4.02%, which consisted of a floating eurodollar base rate of 2.52% plus a margin of 1.50%. However, the Company has interest rate swap contracts that effectively convert the floating eurodollar base rates on amounts outstanding to a fixed base rate.


(2)	The Term loan B facility was completely repaid in 2018.


(3)	The Company had $1.0 billion of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2018.


(4)	Consists of $800.0 million principal amount of Senior Notes outstanding. The Senior Notes pay a fixed rate of 5.125% and mature on April 1, 2025.


(5)	Consists of a State of Connecticut economic development loan with a 3.00% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. The loan may be repaid at any time by the Company without penalty.


(6)	The weighted average annual effective rate on the Company's total debt outstanding for 2018, including the effects of its interest rate swaps discussed below, was 4.17%.


(7)	The contractual due dates of principal amounts by year on the debt outstanding as of December 31, 2018 were as follows: $102.6 million in 2019; $139.7 million in 2020; $37.6 million in 2021; $1.23 billion in 2022; and $800.0 million in 2025.

(8)

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments under Operating Leases

uture minimum annual cash payments under those operating lease agreements as of December 31, 2018 were as follows (in thousands):



Year ended December 31,
2019	$	130,991
2020	121,802
2021	118,945
2022	111,117
2023	106,113
Thereafter	689,360
Total minimum lease payments (1)	$	1,278,328

(1) Excludes approximately $372.0 million of sublease income.

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Schedule of Transactions Relating to Common Stock

The following table summarizes transactions relating to our Common Stock for the three years ended December 31, 2018:



	Issued Shares	Treasury Stock Shares
Balance at December 31, 2015	156,234,415	73,896,245
Issuances under stock plans	—	(923,696	)
Purchases for treasury (1)	—	610,623
Balance at December 31, 2016	156,234,415	73,583,172
Issued in connection with the acquisition of CEB	7,367,652	—
Issuances under stock plans	—	(1,186,150	)
Purchases for treasury (1)	—	382,183
Balance at December 31, 2017	163,602,067	72,779,205
Issuances under stock plans	—	(933,246	)
Purchases for treasury (1), (2)	—	2,054,018
Balance at December 31, 2018	163,602,067	73,899,977


(1)	The Company used a total of $260.8 million, $41.3 million and $59.0 million in cash for share repurchases in 2018, 2017 and 2016, respectively.


(2)	The number of shares repurchased in 2018 includes shares repurchased in December 2018 that settled in January 2019.

Schedule of Accumulated Other Comprehensive (Loss) Income, Net by Components

The following tables disclose information about changes in Accumulated Other Comprehensive Income (Loss) ("AOCI/L") by component and the related amounts reclassified out of AOCI/L to income during the years indicated (net of tax, in thousands) (1):

2018



	Interest Rate Swaps			Defined Benefit Pension Plans			Foreign Currency Translation Adjustments			Total
Balance - December 31, 2017	$	2,483		$	(5,861	)	$	4,886		$	1,508
Adoption of ASU No. 2018-02 (2)	591			—			—			591
Other comprehensive income (loss) activity during the period:
Change in AOCI/L before reclassifications to income	(9,447		)	—			29,066			19,619
Reclassifications from AOCI/L to income (3), (4), (5)	(1,397		)	123			(60,311		)	(61,585		)
Other comprehensive income (loss) for the period	(10,844		)	123			(31,245		)	(41,966		)
Balance - December 31, 2018	$	(7,770	)	$	(5,738	)	$	(26,359	)	$	(39,867	)

2017



	Interest Rate Swaps			Defined Benefit Pension Plans			Foreign Currency Translation Adjustments			Total
Balance - December 31, 2016	$	(1,409	)	$	(5,797	)	$	(42,477	)	$	(49,683	)
Other comprehensive income (loss) activity during the period:
Change in AOCI/L before reclassifications to income	(1,492		)	—			47,363			45,871
Reclassifications from AOCI/L to income (3), (4)	5,384			(64		)	—			5,320
Other comprehensive income (loss) for the period	3,892			(64		)	47,363			51,191
Balance - December 31, 2017	$	2,483		$	(5,861	)	$	4,886		$	1,508

(1) Amounts in parentheses represent debits (deferred losses).

(2) See Note 1 - Business and Significant Accounting Policies for additional information regarding the Company's adoption of ASU No. 2018-02.

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

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+ Details

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Stock-based Compensation Expense by Award Type

The Company recognized the following stock-based compensation expense by award type and expense category line item during the years ended December 31 (in millions):



Award type	2018		2017		2016
Stock appreciation rights	$	6.3	$	5.6	$	5.6
Restricted stock units	59.2		72.6		40.4
Common stock equivalents	0.7		0.7		0.7
Total (1)	$	66.2	$	78.9	$	46.7

Schedule of Stock-based Compensation Expense by Expense Category



Expense category line item	2018		2017		2016
Cost of services and product development	$	28.1	$	25.8	$	21.9
Selling, general and administrative	36.2		35.5		24.8
Acquisition and integration charges (2)	1.9		17.6		—
Total (1)	$	66.2	$	78.9	$	46.7


(1)	Includes charges of $19.4 million, $22.9 million and $19.4 million during 2018, 2017 and 2016, respectively, for awards to retirement-eligible employees. Those awards vest on an accelerated basis.


(2)	These charges are the result of (i) the acceleration of the vesting of certain restricted stock units related to the CEB acquisition and (ii) restricted stock units granted in connection with the CEB integration process.

Schedule of Summary of the Changes in SARS, RSUs, and CSEs Outstanding

The following table summarizes the changes in RSUs outstanding during the year ended December 31, 2018:



	Restricted Stock Units ("RSUs") (in millions)		Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2017	1.5		$	91.47
Granted (1)	0.7		112.96
Vested and released	(0.7	)	88.69
Forfeited	(0.1	)	104.95
Outstanding at December 31, 2018 (2) (3)	1.4		$	101.75

(1)


(2)	The Company expects that substantially all of the RSUs outstanding will vest in future periods.


(3)	As of December 31, 2018, the weighted average remaining contractual term of the RSUs outstanding was approximately 1.1 years.

The following table summarizes changes in SARs outstanding during the year ended December 31, 2018:



	Stock Appreciation Rights ("SARs") (in millions)		Per Share Weighted Average Exercise Price		Per Share Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (Years)
Outstanding at December 31, 2017	1.2		$	76.73	$	17.35	4.28
Granted	0.3		114.26		25.63		6.11
Exercised	(0.3	)	60.67		15.10		n/a
Outstanding at December 31, 2018 (1) (2)	1.2		$	89.45	$	19.88	4.33
Vested and exercisable at December 31, 2018 (2)	0.5		$	75.73	$	17.02	3.24

n/a = not applicable


(1)	As of December 31, 2018, 0.7 million of the total SARs outstanding were unvested. The Company expects that substantially all of those unvested awards will vest in future periods.


(2)	As of December 31, 2018, the total SARs outstanding had an intrinsic value of $46.0 million. On such date, SARs vested and exercisable had an intrinsic value of $26.9 million.

The following table summarizes the changes in CSEs outstanding during the year ended December 31, 2018:



	Common Stock Equivalents ("CSEs")		Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2017	110,013		$	23.19
Granted	5,550		131.49
Converted to shares of Common Stock upon grant	(5,783	)	93.45
Outstanding at December 31, 2018	109,780		$	24.96

Schedule of Fair Value Assumptions of SARS

The fair value of a SARs award is determined on the date of grant using the Black-Scholes-Merton valuation model with the following weighted average assumptions for the years ended December 31:



	2018		2017		2016
Expected dividend yield (1)	—	%	—	%	—	%
Expected stock price volatility (2)	21	%	22	%	22	%
Risk-free interest rate (3)	2.5	%	1.8	%	1.1	%
Expected life in years (4)	4.52		4.53		4.39


(1)	The expected dividend yield assumption was based on both the Company's historical and anticipated dividend payouts. Historically, the Company has not paid cash dividends on its Common Stock.


(2)	The determination of expected stock price volatility was based on both historical Common Stock prices and implied volatility from publicly traded options in the Common Stock.


(3)	The risk-free interest rate was based on the yield of a U.S. Treasury security with a maturity similar to the expected life of the award.


(4)	The expected life represents the Company’s estimate of the weighted average period of time the SARs are expected to be outstanding (that is, the period between the service inception date and the expected exercise date).

Computation of Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Schedule of Reconciliation of the Basic and Diluted Earnings Per Share Computations

The following table sets forth the calculation of basic and diluted earnings per share for the three years ended December 31 (in thousands, except per share data):



	2018		2017		2016
Numerator:
Net income used for calculating basic and diluted earnings per common share	$	122,456	$	3,279	$	193,582
Denominator: (1)
Weighted average common shares used in the calculation of basic earnings per share	90,827		88,466		82,571
Common share equivalents associated with stock-based compensation plans	1,295		1,324		1,249
Shares used in the calculation of diluted earnings per share	92,122		89,790		83,820
Earnings per share: (2)
Basic	$	1.35	$	0.04	$	2.34
Diluted	$	1.33	$	0.04	$	2.31


(1)	The Company repurchased 2.1 million, 0.4 million and 0.6 million shares of its Common Stock in 2018, 2017 and 2016, respectively.


(2)	Both basic and diluted earnings per share for 2017 include a tax benefit of approximately $0.66 per share related to the U.S. Tax Cuts and Jobs Act of 2017. Note 10 — Income Taxes provides information about the Company's income taxes.

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share



	2018		2017		2016
Anti-dilutive common share equivalents as of December 31 (in millions): (a)	—		0.3		0.2
Average market price per share of Common Stock during the year	$	135.60	$	116.09	$	92.58

(a) Anti-dilutive common shares for 2018 were minimal.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Components of Income before Income Taxes

The following is a summary of the components of the Company's income (loss) before income taxes for the years ended December 31 (in thousands):



	2018		2017			2016
U.S.	$	34,159	$	(135,757	)	$	182,178
Non-U.S.	146,962		7,940			106,253
Income (loss) before income taxes	$	181,121	$	(127,817	)	$	288,431

Schedule of Components of Income Tax

The expense (benefit) for income taxes on the above income consists of the following components (in thousands):



	2018			2017			2016
Current tax expense:
U.S. federal	$	2,817		$	48,339		$	58,616
State and local	6,969			434			11,292
Foreign	45,042			38,602			27,536
Total current	54,828			87,375			97,444
Deferred tax (benefit) expense:
U.S. federal	12,462			(176,046		)	(61		)
State and local	1,258			(14,363		)	(349		)
Foreign	(13,795		)	(25,898		)	(1,626		)
Total deferred	(75		)	(216,307		)	(2,036		)
Total current and deferred	54,753			(128,932		)	95,408
Benefit (expense) relating to interest rate swaps used to increase (decrease) equity	3,840			(2,477		)	(1,113		)
Benefit from stock transactions with employees used to increase equity	58			46			52
Benefit relating to defined-benefit pension adjustments used to increase equity	14			267			502
Total tax expense (benefit)	$	58,665		$	(131,096	)	$	94,849

Schedule of Deferred Tax Assets and Liabilities

Long-term deferred tax assets and liabilities are comprised of the following (in thousands):



	December 31,
	2018			2017
Accrued liabilities	$	96,292		$	80,557
Loss and credit carryforwards	14,830			59,502
Assets relating to equity compensation	19,653			24,874
Other assets	14,092			30,236
Gross deferred tax assets	144,867			195,169
Property, equipment, and leasehold improvements	(3,421		)	(962		)
Intangible assets	(214,580		)	(372,542		)
Prepaid expenses	(41,926		)	(35,126		)
Other liabilities	(61,068		)	(6,584		)
Gross deferred tax liabilities	(320,995		)	(415,214		)
Valuation allowance	(4,066		)	(3,192		)
Net deferred tax liabilities	$	(180,194	)	$	(223,237	)

Schedule of Effective Income Tax Rate Reconciliation

The differences between the U.S. federal statutory income tax rate and the Company’s effective tax rate on income before income taxes for the years ended December 31 follow:



	2018		2017		2016
Statutory tax rate	21.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	—		3.6		2.3
Effect of non-U.S. operations	(10.6	)	5.9		(6.1	)
Change in the reserve for tax contingencies	15.7		(2.8	)	3.2
Law changes	(1.3	)	41.8		—
Stock-based compensation expense	(5.3	)	11.0		(3.8	)
Nondeductible acquisition costs	0.9		(7.9	)	2.6
Nondeductible meals and entertainment costs	2.7		(3.5	)	1.1
Gains/Losses on divested operations and held-for-sale assets	12.2		13.1		—
Limitation on executive compensation	2.7		(0.1	)	—
Foreign-derived intangible income	(2.0	)	—		—
Change in the valuation allowance	0.5		3.0		(0.2	)
Goodwill	(3.8	)	—		—
Other items, net	(0.3	)	3.5		(1.2	)
Effective tax rate	32.4	%	102.6	%	32.9	%

Schedule of Reconciliation of Beginning and Ending Unrecognized Tax Benefits

The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding interest and penalties, for the years ended December 31 (in thousands):



	2018			2017
Beginning balance	$	60,269		$	37,099
Additions based on tax positions related to the current year	27,371			10,883
Additions for tax positions of prior years	14,691			24,299
Reductions for tax positions of prior years	(3,939		)	(10,613		)
Reductions for expiration of statutes	(6,293		)	(1,368		)
Settlements	(472		)	(1,769		)
Change in foreign currency exchange rates	(1,278		)	1,738
Ending balance	$	90,349		$	60,269

Derivatives and Hedging (Tables)

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Notional Amounts of Outstanding Derivative Positions

The following tables provide information regarding the Company’s outstanding derivatives contracts as of the dates indicated (in thousands, except for number of contracts):

December 31, 2018



Derivative Contract Type	Number of Contracts	Notional Amounts		Fair Value Asset (Liability), Net (3)			Balance Sheet Line Item	Unrealized Loss Recorded in AOCI/L
Interest rate swaps (1)	7	$	2,100,000	$	(10,681	)	Other liabilities	$	(7,770	)
Foreign currency forwards (2)	135	927,375		(1,942		)	Accrued liabilities	—
Total	142	$	3,027,375	$	(12,623	)		$	(7,770	)

December 31, 2017



Derivative Contract Type	Number of Contracts	Notional Amounts		Fair Value Asset (Liability), Net (3)		Balance Sheet Line Item	Unrealized Gain Recorded in AOCI/L
Interest rate swaps (1)	5	$	1,400,000	$	3,412	Other assets	$	2,483
Foreign currency forwards (2)	137	686,764		448		Other current assets	—
Total	142	$	2,086,764	$	3,860		$	2,483


(1)	The swaps have been designated and are accounted for as cash flow hedges of the forecasted interest payments on borrowings. As a result, changes in the fair value of the swaps are deferred and are recorded in AOCI/L, net of tax effect. Note 5 — Debt provides additional information.

(2)


(3)	See Note 12 — Fair Value Disclosures for the determination of the fair value of these instruments.

Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance

The following table provides information regarding amounts recognized in the Consolidated Statements of Operations for derivative contracts for the years ended December 31 (in millions):



Amount recorded in:	2018			2017			2016
Interest (income) expense, net (1)	$	(1.9	)	$	7.9		$	7.6
Other expense (income), net (2)	10.4			(0.8		)	0.3
Total expense, net	$	8.5		$	7.1		$	7.9


(1)	Consists of interest (income) expense from interest rate swap contracts.


(2)	Consists of net realized and unrealized gains and losses on foreign currency forward contracts.

Fair Value Disclosures (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured to Fair Value on Recurring Basis

The following table presents the fair value of certain financial assets and liabilities (in thousands):



Description:	December 31, 2018		December 31, 2017
Assets:
Values based on Level 1 inputs:
Deferred compensation plan assets (1)	$	8,956	$	29,108
Total Level 1 inputs	8,956		29,108
Values based on Level 2 inputs:
Deferred compensation plan assets (1)	57,690		59,017
Foreign currency forward contracts (2)	1,318		2,053
Interest rate swap contracts (3)	—		3,412
Total Level 2 inputs	59,008		64,482
Total Assets	$	67,964	$	93,590
Liabilities:
Values based on Level 2 inputs:
Deferred compensation plan liabilities (1)	$	68,570	$	89,900
Foreign currency forward contracts (2)	3,260		1,605
Interest rate swap contracts (3)	10,681		—
Senior Notes due 2025 (4)	776,160		837,560
Total Level 2 inputs	858,671		929,065
Total Liabilities	$	858,671	$	929,065

(1)


(2)	The Company enters into foreign currency forward exchange contracts to hedge the effects of adverse fluctuations in foreign currency exchange rates (see Note 11 — Derivatives and Hedging). Valuation of these contracts is based on observable foreign currency exchange rates in active markets, which the Company considers a Level 2 input.

(3)


(4)	As discussed in Note 5 — Debt, the Company has $800.0 million of principal amount fixed-rate Senior Notes due in 2025. The estimated fair value of the notes was derived from quoted market prices provided by an independent dealer, which the Company considers to be a Level 2 input.

Employee Benefits (Tables)

12 Months Ended

Dec. 31, 2018

Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]

Schedule of Components of Defined Benefit Pension Expense

The following are the components of defined benefit pension plan expense for the years ended December 31 (in thousands):



	2018			2017			2016
Service cost	$	3,145		$	2,820		$	2,780
Interest cost	840			765			850
Expected return on plan assets	(475		)	(360		)	(375		)
Recognition of actuarial loss	340			350			200
Total defined benefit pension plan expense	$	3,850		$	3,575		$	3,455

Schedule of Assumptions Used in the Computation of Pension Expense

The following are the key assumptions used in the computation of pension expense for the years ended December 31:



	2018		2017		2016
Weighted average discount rate (1)	1.81	%	1.78	%	1.78	%
Average compensation increase	2.58	%	2.66	%	2.67	%


(1)	Discount rates are typically determined by utilizing the yields on long-term corporate or government bonds in the relevant country with a duration consistent with the expected term of the underlying pension obligations.

Schedule of Changes in the Projected Benefit Obligation

The following table provides information related to changes in the projected benefit obligation for the years ended December 31 (in thousands):



	2018			2017			2016
Projected benefit obligation at beginning of year	$	45,450		$	38,400		$	35,870
Service cost	3,145			2,820			2,780
Interest cost	840			765			850
Actuarial loss (gain) due to assumption changes and plan experience	(430		)	690			1,480
Additions and contractual termination benefits	(950		)	(860		)	—
Benefits paid (1)	(1,400		)	(920		)	(1,640		)
Foreign currency impact	(1,765		)	4,555			(940		)
Projected benefit obligation at end of year (2)	$	44,890		$	45,450		$	38,400


(1)	The Company projects the following benefit payments will be made in future years directly to plan participants: $1.2 million in 2019; $1.5 million in 2020; $1.6 million in 2021; $1.7 million in 2022; $2.1 million in 2023; and $12.1 million in total in the five years thereafter.


(2)	Measured as of December 31.

Schedule of Funded Status of the Plans and Related Amounts Recorded in Consolidated Balance Sheet

The following table provides information regarding the funded status of the plans and related amounts recorded in the Company’s Consolidated Balance Sheets as of December 31 (in thousands):



Funded status of the plans:	2018			2017			2016
Projected benefit obligation	$	44,890		$	45,450		$	38,400
Pension plan assets at fair value (1)	(19,460		)	(18,475		)	(14,465		)
Funded status – shortfall (2)	$	25,430		$	26,975		$	23,935



Amounts recorded in the Consolidated Balance Sheets for the plans:
Other liabilities — accrued pension obligation (2)	$	25,430		$	26,975		$	23,935
Stockholders’ equity — deferred actuarial loss (3)	$	(5,738	)	$	(5,861	)	$	(5,797	)

(1)


(2)	The Funded status - shortfall represents the amount of the projected benefit obligation that the Company has not funded with a third-party trustee. This amount is a liability of the Company and is recorded in Other liabilities on the Company’s Consolidated Balance Sheets.

(3)

Segment Information (Tables)

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Schedule of Segment Reporting Information by Segment

The following tables present information about the Company’s reportable segments for the periods indicated (in thousands):



	Research		Conferences		Consulting		Other		Consolidated
2018
Revenues	$	3,105,764	$	410,461	$	353,667	$	105,562	$	3,975,454
Gross contribution	2,144,097		207,260		102,541		65,075		2,518,973
Corporate and other expenses									(2,259,258		)
Operating income									$	259,715

	Research		Conferences		Consulting		Other		Consolidated
2017
Revenues	$	2,471,280	$	337,903	$	327,661	$	174,650	$	3,311,494
Gross contribution	1,653,014		163,480		93,643		90,249		2,000,386
Corporate and other expenses									(2,006,715		)
Operating loss									$	(6,329	)

	Research		Conferences		Consulting		Other		Consolidated
2016
Revenues	$	1,857,001	$	268,605	$	318,934	$	—	$	2,444,540
Gross contribution	1,285,611		136,655		89,734		—		1,512,000
Corporate and other expenses									(1,206,859		)
Operating income									$	305,141

Schedule of Reconciliation of Segment Gross Contribution to Net Income

The following table provides a reconciliation of total segment gross contribution to net income for the years ended December 31 (in thousands):



	2018		2017			2016
Total segment gross contribution	$	2,518,973	$	2,000,386		$	1,512,000
Costs and expenses:
Cost of services and product development - unallocated (1)	12,319		9,090			13,108
Selling, general and administrative	1,884,141		1,599,004			1,089,184
Depreciation and amortization	255,601		240,171			61,969
Acquisition and integration charges	107,197		158,450			42,598
Operating income (loss)	259,715		(6,329		)	305,141
Interest expense and other, net	124,041		121,488			16,710
Gain from divested operations	45,447		—			—
Provision (benefit) for income taxes	58,665		(131,096		)	94,849
Net income	$	122,456	$	3,279		$	193,582


(1)	The unallocated amounts consist of certain bonus and related fringe costs recorded in consolidated Cost of services and product development expense that are not allocated to segment expense. The Company's policy is to only allocate bonus and related fringe charges to segments for up to 100% of the segment employee's target bonus. Amounts above 100% are absorbed by corporate.

Schedule of Revenue from External Customers and Long-Lived Assets by Geographical Areas



	2018		2017		2016
Long-lived assets: (1)
United States and Canada	$	305,928	$	288,735	$	143,921
Europe, Middle East and Africa	67,306		84,840		42,326
Other International	50,800		41,674		24,630
Total long-lived assets	$	424,034	$	415,249	$	210,877


(1)	Excludes goodwill, intangible assets and held-for-sale assets.

Valuation and Qualifying Accounts (Tables)

12 Months Ended

Dec. 31, 2018

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

Summary of Valuation Allowance

The following table summarizes activity in the Company’s allowance for losses for the years ended December 31 (in thousands):



	Balance at Beginning of Year		Additions Charged to Expense		Additions Charged Against Revenues		Deductions from Reserve			Reclassification to Accounts Payable and Accrued Liabilities			Balance at End of Year
2018:
Bad debt allowance (1)	$	12,700	$	12,500	$	—	$	(11,300	)	$	(6,200	)	$	7,700
2017:
Bad debt allowance and revenue reserve (1)	$	7,400	$	16,600	$	5,500	$	(16,800	)	$	—		$	12,700
2016:
Bad debt allowance and revenue reserve	$	6,900	$	4,750	$	4,850	$	(9,100	)	$	—		$	7,400

Business and Significant Accounting Policies - Additional Information (Details) enterprise in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) segment country enterprise	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business and Significant Accounting Policies [Line Items]
Amortization of deferred sales commissions, amortization period	1 year
Number of enterprises served \| enterprise	15
Number of countries in which entity operates \| country	100
Number of reportable segments \| segment	3
Acquisition and integration charges	$ 107,197	$ 158,450	$ 42,598
Stock-based compensation expense	66,172	78,943	46,661
Rent expense	93,500	87,900	38,000
Depreciation expense	68,592	63,897	37,172
Net capitalized development costs for internal use software	37,400	26,900
Amortization of capitalized internal software development costs	13,200	9,900	8,800
Amortization of intangibles	187,009	176,274	24,797
Pension expense	3,900	3,600	3,500
Long-term debt, gross	2,312,092	3,323,062
Foreign currency transaction gain (loss)	9,200	(5,500)	(400)
Derivative instruments, gain (loss) recognized in income, net	8,500	7,100	7,900
Payments for purchases of treasury stock	260,832	41,272	58,961
Foreign currency exchange contracts
Business and Significant Accounting Policies [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ (10,400)	$ 800	(300)
Customer Relationships \| Minimum
Business and Significant Accounting Policies [Line Items]
Remaining amortization period	4 years
Customer Relationships \| Maximum
Business and Significant Accounting Policies [Line Items]
Remaining amortization period	13 years
Software \| Minimum
Business and Significant Accounting Policies [Line Items]
Remaining amortization period	3 years
Software \| Maximum
Business and Significant Accounting Policies [Line Items]
Remaining amortization period	7 years
Content \| Minimum
Business and Significant Accounting Policies [Line Items]
Remaining amortization period	1 year 6 months
Content \| Maximum
Business and Significant Accounting Policies [Line Items]
Remaining amortization period	5 years
Non-Compete \| Minimum
Business and Significant Accounting Policies [Line Items]
Remaining amortization period	2 years
Non-Compete \| Maximum
Business and Significant Accounting Policies [Line Items]
Remaining amortization period	5 years
ASU 2016-09
Business and Significant Accounting Policies [Line Items]
Adoption of ASU				$ (261)
ASU 2016-09 \| Accumulated Earnings
Business and Significant Accounting Policies [Line Items]
Adoption of ASU				$ (261)
ASU 2016-09 \| Pro Forma \| Accumulated Earnings
Business and Significant Accounting Policies [Line Items]
Adoption of ASU			$ (300)

Business and Significant Accounting Policies - Property, Equipment and Leasehold Improvements, Less Accumulated Depreciation and Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 514,362	$ 432,019
Less — accumulated depreciation and amortization	(246,697)	(210,512)
Property, equipment and leasehold improvements, net	267,665	221,507
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 210,955	189,015
Computer equipment and software \| Minimum
Property, Plant and Equipment [Line Items]
Useful Life	2 years
Computer equipment and software \| Maximum
Property, Plant and Equipment [Line Items]
Useful Life	7 years
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 85,002	67,288
Furniture and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Furniture and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful Life	8 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 218,405	$ 175,716
Leasehold improvements \| Minimum
Property, Plant and Equipment [Line Items]
Useful Life	2 years
Leasehold improvements \| Maximum
Property, Plant and Equipment [Line Items]
Useful Life	15 years

Business and Significant Accounting Policies - Intangible Assets Subject to Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-lived Intangible Assets [Roll Forward]
Gross cost	$ 1,482,982	$ 116,767
Divestitures	(46,129)
Additions due to acquisitions		1,600,190
Write-off of fully amortized intangible assets	(15,998)	(4,227)
Reclassified as held-for-sale		(250,472)
Foreign currency translation impact	(27,994)	20,724
Gross cost	1,392,861	1,482,982
Accumulated amortization	(350,296)	(190,960)
Finite-lived intangible assets, net	1,042,565	1,292,022
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost	1,200,316	63,369
Divestitures	(45,175)
Additions due to acquisitions		1,253,312
Write-off of fully amortized intangible assets	(303)	0
Reclassified as held-for-sale		(140,156)
Foreign currency translation impact	(23,182)	23,791
Gross cost	1,131,656	1,200,316
Accumulated amortization	(184,918)	(92,983)
Finite-lived intangible assets, net	946,738	1,107,333
Software
Finite-lived Intangible Assets [Roll Forward]
Gross cost	123,424	16,025
Divestitures	(321)
Additions due to acquisitions		180,787
Write-off of fully amortized intangible assets	(11,715)	0
Reclassified as held-for-sale		(69,012)
Foreign currency translation impact	(687)	(4,376)
Gross cost	110,701	123,424
Accumulated amortization	(38,901)	(26,344)
Finite-lived intangible assets, net	71,800	97,080
Content
Finite-lived Intangible Assets [Roll Forward]
Gross cost	104,313	3,728
Divestitures	(473)
Additions due to acquisitions		141,707
Write-off of fully amortized intangible assets	(669)	(4,227)
Reclassified as held-for-sale		(38,593)
Foreign currency translation impact	(4,329)	1,698
Gross cost	98,842	104,313
Accumulated amortization	(92,717)	(47,475)
Finite-lived intangible assets, net	6,125	56,838
Other
Finite-lived Intangible Assets [Roll Forward]
Gross cost	54,929	33,645
Divestitures	(160)
Additions due to acquisitions		24,384
Write-off of fully amortized intangible assets	(3,311)	0
Reclassified as held-for-sale		(2,711)
Foreign currency translation impact	204	(389)
Gross cost	51,662	54,929
Accumulated amortization	(33,760)	(24,158)
Finite-lived intangible assets, net	$ 17,902	$ 30,771

Business and Significant Accounting Policies - Estimated Future Amortization Expense by Year from Purchased Intangibles (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2019	$ 129,394
2020	122,756
2021	102,338
2022	92,801
2023 and thereafter	595,276
Finite-lived intangible assets, net	$ 1,042,565	$ 1,292,022

Business and Significant Accounting Policies - Changes to the Carrying Amount of Goodwill by Reporting Unit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Beginning Balance	$ 2,987,294	$ 738,453
Additions due to acquisition		2,457,791
Reclassified as held-for-sale		(212,994)
Foreign currency translation impact and other	28,420	4,044
Ending Balance	2,923,136	2,987,294
Not Discontinued Operations
Goodwill [Roll Forward]
Additions due to acquisitions	(92,578)
Research
Goodwill [Roll Forward]
Beginning Balance	2,619,677	595,450
Additions due to acquisition		2,042,514
Reclassified as held-for-sale		0
Foreign currency translation impact and other	21,241	(18,287)
Ending Balance	2,638,418	2,619,677
Research \| Not Discontinued Operations
Goodwill [Roll Forward]
Additions due to acquisitions	(2,500)
Conferences
Goodwill [Roll Forward]
Beginning Balance	187,920	46,523
Additions due to acquisition		140,914
Reclassified as held-for-sale		0
Foreign currency translation impact and other	(266)	483
Ending Balance	187,654	187,920
Conferences \| Not Discontinued Operations
Goodwill [Roll Forward]
Additions due to acquisitions	0
Consulting
Goodwill [Roll Forward]
Beginning Balance	97,798	96,480
Additions due to acquisition		0
Reclassified as held-for-sale		0
Foreign currency translation impact and other	(734)	1,318
Ending Balance	97,064	97,798
Consulting \| Not Discontinued Operations
Goodwill [Roll Forward]
Additions due to acquisitions	0
Other
Goodwill [Roll Forward]
Beginning Balance	81,899	0
Additions due to acquisition		274,363
Reclassified as held-for-sale		(212,994)
Foreign currency translation impact and other	8,179	20,530
Ending Balance	0	$ 81,899
Other \| Not Discontinued Operations
Goodwill [Roll Forward]
Additions due to acquisitions	$ (90,078)

Business and Significant Accounting Policies - Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 156,368	$ 538,908	$ 474,233	$ 372,976
Restricted cash classified in:
Prepaid expenses and other current assets	2,295	15,148	25,121	13,505
Other assets	0	3,002	0	25,626
Cash and cash equivalents	0	10,000	0	0
Cash and cash equivalents and restricted cash	$ 158,663	$ 567,058	$ 499,354	$ 412,107

Business and Significant Accounting Policies - New ASU Narrative (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2015 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in cash used in investing activities		$ 384,051	$ (2,752,545)	$ (98,059)
Total cash amount		158,663	567,058	499,354			$ 412,107
Income tax benefit		$ (58,665)	131,096	(94,849)
Number of reportable segments \| segment		3
Revenue recognized previously attributable to deferred revenues		$ 1,287,800
Revenue reserve balance		$ 7,400
Amortization of deferred sales commissions, amortization period		1 year
Amortization of deferred sales commissions		$ 304,800	230,500	180,200
ASU 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from AOCI to earnings	$ 600
ASU 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASU			(13,717)
Income tax benefit		$ 6,800
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage of subscription contracts billable upon signing for twelve months of service		75.00%
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage of subscription contracts billable upon signing for twelve months of service		80.00%
Accumulated Earnings \| ASU 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASU			(591)
Accumulated Earnings \| ASU 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASU			(13,717)			$ (13,700)
Product Concentration Risk \| Research \| Sales Revenue, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk percentage		90.00%
Restatement Adjustment \| ASU 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in cash used in investing activities			7,000	14,000
Total cash amount			$ 18,200	$ 25,100			$ 39,100
Subsequent Event \| Minimum \| ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liability					$ 835,000
ROU asset					637,000
Subsequent Event \| Maximum \| ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liability					855,000
ROU asset					$ 657,000

Business and Significant Accounting Policies - Impact of Adoption of ASU 2014-09 (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fees receivable	$ (1,255,118)		$ (1,176,843)
Prepaid expenses and other current assets	165,237		124,632
Allowance for doubtful accounts	(7,700)		(12,700)
Accounts payable and accrued liabilities	$ 710,113		$ 666,821
Accounting Standards Update 2014-09 \| Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fees receivable		$ 26,700
Prepaid expenses and other current assets		26,700
Allowance for doubtful accounts		6,200
Accounts payable and accrued liabilities		$ 6,200

Business and Significant Accounting Policies - Disaggregation of Revenue by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total revenues	$ 3,975,454	$ 3,311,494	$ 2,444,540
Research
Disaggregation of Revenue [Line Items]
Total revenues	3,105,764	2,471,280	1,857,001
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	410,461	337,903	268,605
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	353,667	327,661	318,934
Other
Disaggregation of Revenue [Line Items]
Total revenues	105,562	174,650	0
United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	2,514,952	2,092,366	1,519,748
United States and Canada \| Research
Disaggregation of Revenue [Line Items]
Total revenues	1,994,016	1,600,847	1,178,575
United States and Canada \| Conferences
Disaggregation of Revenue [Line Items]
Total revenues	256,219	210,698	162,162
United States and Canada \| Consulting
Disaggregation of Revenue [Line Items]
Total revenues	205,874	188,022	179,011
United States and Canada \| Other
Disaggregation of Revenue [Line Items]
Total revenues	58,843	92,799	0
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	1,000,490	855,421	616,721
Europe, Middle East and Africa \| Research
Disaggregation of Revenue [Line Items]
Total revenues	737,129	597,943	434,753
Europe, Middle East and Africa \| Conferences
Disaggregation of Revenue [Line Items]
Total revenues	105,909	86,567	72,926
Europe, Middle East and Africa \| Consulting
Disaggregation of Revenue [Line Items]
Total revenues	119,258	111,792	109,042
Europe, Middle East and Africa \| Other
Disaggregation of Revenue [Line Items]
Total revenues	38,194	59,119	0
Other International
Disaggregation of Revenue [Line Items]
Total revenues	460,012	363,707	308,071
Other International \| Research
Disaggregation of Revenue [Line Items]
Total revenues	374,619	272,490	243,673
Other International \| Conferences
Disaggregation of Revenue [Line Items]
Total revenues	48,333	40,638	33,517
Other International \| Consulting
Disaggregation of Revenue [Line Items]
Total revenues	28,535	27,847	30,881
Other International \| Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 8,525	$ 22,732	$ 0

Business and Significant Accounting Policies - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total revenues	$ 3,975,454	$ 3,311,494	$ 2,444,540
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	3,232,240	2,686,428	1,978,595
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	743,214	625,066	465,945
Research
Disaggregation of Revenue [Line Items]
Total revenues	3,105,764	2,471,280	1,857,001
Research \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	2,851,176	2,275,377	1,710,786
Research \| Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	254,588	195,903	146,215
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	410,461	337,903	268,605
Conferences \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Conferences \| Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	410,461	337,903	268,605
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	353,667	327,661	318,934
Consulting \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	294,397	269,720	267,809
Consulting \| Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	59,270	57,941	51,125
Other
Disaggregation of Revenue [Line Items]
Total revenues	105,562	174,650	0
Other \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	86,667	141,331	0
Other \| Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 18,895	$ 33,319	$ 0

Business and Significant Accounting Policies - Revenue Remaining Performance Obligation (Details) $ in Millions	Dec. 31, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue, remaining performance obligation	$ 2,700.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue, remaining performance obligation	1,620.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue, remaining performance obligation	874.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue, remaining performance obligation	$ 186.5

Business and Significant Accounting Policies - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets:
Fees receivable, gross	$ 1,262,818	$ 1,162,871
Contract assets	26,119	26,672
Contract liabilities:
Deferred revenues (current liability)	1,745,244	1,630,198
Non-current deferred revenues	21,194	16,205
Total contract liabilities	1,766,438	1,646,403
Revenue recognized previously attributable to deferred revenues	1,287,800
Revenue reserve balance	$ 7,400
Amortization of deferred sales commissions, amortization period	1 year
Amortization of deferred sales commissions	$ 304,800	$ 230,500	$ 180,200

Acquisitions and Divestiture - Additional Information (Details) $ in Thousands					3 Months Ended		12 Months Ended			21 Months Ended
	Apr. 05, 2017 USD ($) employee country	Mar. 09, 2017 USD ($) employee	Nov. 09, 2016 USD ($) employee	Jun. 28, 2016 USD ($) employee	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2018 USD ($) country	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($) country
Business Acquisition [Line Items]
Acquisition and integration charges							$ 107,197	$ 158,450	$ 42,598
Percentage of voting interests acquired					100.00%			100.00%
Number of countries in which entity operates \| country							100			100
Net cash paid for acquisition					$ 2,640,000		$ 15,855	$ 2,641,780	48,196
Goodwill					$ 2,987,294		2,923,136	2,987,294	738,453	$ 2,923,136
CEB
Business Acquisition [Line Items]
Charges and adjustments							69,790	13,087		82,900
Payments							26,087	126		26,200
Exit costs							90,600			$ 90,600
Percentage of voting interests acquired	100.00%
Consideration transferred, aggregate purchase price	$ 3,518,829
Consideration transferred, cash paid	2,687,704					$ 12,500
Fair value of Gartner equity	$ 818,660
Entity number of employees \| employee	4,900
Number of countries in which entity operates \| country	70
Proceeds from issuance of debt	$ 2,800,000
Goodwill	2,349,589
Finite-lived intangible assets	1,584,300
Accounts payable and accrued liabilities	142,134
Liabilities assumed	$ 957,033
L2, Inc.
Business Acquisition [Line Items]
Percentage of voting interests acquired		100.00%
Consideration transferred, aggregate purchase price		$ 134,199
Consideration transferred, cash paid		134,199
Fair value of Gartner equity		$ 0
Entity number of employees \| employee		150
Goodwill		$ 108,202
Finite-lived intangible assets		15,890
Accounts payable and accrued liabilities		3,050
Liabilities assumed		$ 17,919
Machina Research Limited And SCM World
Business Acquisition [Line Items]
Goodwill, purchase accounting adjustments									1,900
Goodwill									32,400
Finite-lived intangible assets									$ 5,900
Machina Research
Business Acquisition [Line Items]
Percentage of voting interests acquired			100.00%
Consideration transferred, cash paid			$ 4,500
Entity number of employees \| employee			16
SCM World
Business Acquisition [Line Items]
Percentage of voting interests acquired				100.00%
Consideration transferred, cash paid				$ 34,200
Entity number of employees \| employee				60
Net cash paid for acquisition				$ 27,900
Disposed of by Sale \| CEB
Business Acquisition [Line Items]
Charges and adjustments							$ 7,500	$ (10,100)

Acquisitions and Divestiture - Summary of Exited Space Liability (Details) - CEB - USD ($) $ in Thousands	12 Months Ended		21 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018
Liability Related to Exited Space [Roll Forward]
Beginning liability balance	$ 12,961	$ 0
Charges and adjustments	69,790	13,087	$ 82,900
Payments	(26,087)	(126)	(26,200)
Ending liability balance	56,664	$ 12,961	$ 56,664
Sublease income	$ 2,515

Acquisitions and Divestiture - Summary of Consideration Transferred (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Apr. 05, 2017	Mar. 09, 2017	Sep. 30, 2017	Dec. 31, 2017
CEB and L2 Acquisitions
Business Acquisition [Line Items]
Cash paid at close				$ 2,821,903
Additional cash paid				12,465
Fair value of Gartner equity				818,660
Total aggregate consideration				$ 3,653,028
CEB
Business Acquisition [Line Items]
Cash paid at close	$ 2,687,704		$ 12,500
Additional cash paid	12,465
Fair value of Gartner equity	818,660
Total aggregate consideration	$ 3,518,829
L2, Inc.
Business Acquisition [Line Items]
Cash paid at close		$ 134,199
Additional cash paid		0
Fair value of Gartner equity		0
Total aggregate consideration		$ 134,199

Acquisitions and Divestiture - Summary of the Allocation of the Purchase Price to the Fair Value of the Assets and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Apr. 05, 2017	Mar. 09, 2017	Dec. 31, 2016
Assets:
Goodwill	$ 2,923,136	$ 2,987,294			$ 738,453
CEB and L2 Acquisitions
Assets:
Cash	199,558
Fees receivable	183,717
Prepaid expenses and other current assets	54,777
Property, equipment and leasehold improvements	52,062
Goodwill	2,457,791
Finite-lived intangible assets	1,600,190
Other assets	79,885
Total assets	4,627,980
Liabilities:
Accounts payable and accrued liabilities	145,184
Deferred revenues (current)	259,672
Other liabilities	570,096
Total liabilities	974,952
Net assets acquired	$ 3,653,028
CEB
Assets:
Cash			$ 194,706
Fees receivable			175,440
Prepaid expenses and other current assets			53,610
Property, equipment and leasehold improvements			51,399
Goodwill			2,349,589
Finite-lived intangible assets			1,584,300
Other assets			66,818
Total assets			4,475,862
Liabilities:
Accounts payable and accrued liabilities			142,134
Deferred revenues (current)			246,472
Other liabilities			568,427
Total liabilities			957,033
Net assets acquired			$ 3,518,829
L2, Inc.
Assets:
Cash				$ 4,852
Fees receivable				8,277
Prepaid expenses and other current assets				1,167
Property, equipment and leasehold improvements				663
Goodwill				108,202
Finite-lived intangible assets				15,890
Other assets				13,067
Total assets				152,118
Liabilities:
Accounts payable and accrued liabilities				3,050
Deferred revenues (current)				13,200
Other liabilities				1,669
Total liabilities				17,919
Net assets acquired				$ 134,199

Acquisitions and Divestiture - Proforma (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition, Pro Forma Information [Abstract]
Pro forma diluted income (loss) per share (in dollars per share)	$ 1.66	$ (2.68)
CEB
Business Acquisition, Pro Forma Information [Abstract]
Pro forma total revenue		$ 3,726,470	$ 3,183,070
Pro forma net income (loss)		$ 150,167	$ (241,423)
Pro forma basic income (loss) per share (in dollars per share)		$ 1.66	$ (2.68)

Acquisitions and Divestiture - Disposals (Details) $ in Thousands				12 Months Ended
	Aug. 01, 2018 USD ($)	May 01, 2018 USD ($)	Apr. 03, 2018 USD ($)	Dec. 31, 2018 USD ($) business	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal				$ 45,447	$ 0	$ 0
Held-for-sale \| CEB Talent Assessment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of businesses sold \| business				3
Divestiture, revenue contributed				$ 97,300
Divestiture, operating income (loss)				60,500
Proceeds from divestiture of businesses			$ 375,800
Sale of business, consideration			403,000
Gain on disposal			$ 15,500
Held-for-sale \| CEB Challenger
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses	$ 116,000
Sale of business, consideration	119,100
Gain on disposal	$ 8,300
Held-for-sale \| CEB Workforce Survey and Analytics
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses		$ 26,400
Sale of business, consideration		28,000
Gain on disposal		$ 8,800
Disposed of by Sale \| Other Certain Assets In CEB Transaction [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of assets				8,600
Gain on sale of assets				$ 12,800

Other Assets - Composition of Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Benefit plan-related assets	$ 75,653	$ 97,525
Non-current deferred tax assets	34,494	31,067
Other	46,222	65,150
Total other assets	$ 156,369	$ 193,742

Accounts Payable, Accrued, and Other Liabilities - Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accounts payable	$ 37,508	$ 49,000
Payroll and employee benefits payable	143,803	120,278
Severance and retention bonus payable	28,292	44,685
Bonus payable	170,719	162,710
Commissions payable	126,844	108,969
Taxes payable	19,725	46,758
Other accrued liabilities	183,222	134,421
Total accounts payable and accrued liabilities	$ 710,113	$ 666,821

Accounts Payable, Accrued, and Other Liabilities - Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Non-current deferred revenue	$ 21,194	$ 16,205
Long-term taxes payable	66,304	66,386
Benefit plan-related liabilities	96,033	118,868
Lease-related matters	165,374	115,840
Non-current deferred tax liabilities	214,687	206,338
Other	50,081	54,362
Total other liabilities	$ 613,673	$ 577,999

Debt - 2016 Credit Agreement (Details)			12 Months Ended
Debt - 2016 Credit Agreement (Details)	Apr. 05, 2017 USD ($) installment amendment	Mar. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Long-term debt, gross			$ 3,323,062,000		$ 2,312,092,000
Federal Funds rate
Debt Instrument [Line Items]
Additional interest above federal fund rate				0.50%
2016 Credit Facility Agreement
Debt Instrument [Line Items]
Number of debt agreement amendments \| amendment	3
Debt instrument, interest, additional interest above eurodollar rate	1.00%
2016 Credit Facility Agreement \| Federal Funds rate
Debt Instrument [Line Items]
Minimum applicable margin rate	0.125%
Maximum applicable margin rate	1.50%
2016 Credit Facility Agreement \| Euro Dollar rate
Debt Instrument [Line Items]
Minimum applicable margin rate	1.125%
Maximum applicable margin rate	2.50%
Term loan
Debt Instrument [Line Items]
Long-term debt, gross			1,429,312,000		1,355,062,000
Term B facility
Debt Instrument [Line Items]
Long-term debt, gross			496,250,000		0
Senior notes
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 800,000,000
Long-term debt, gross			800,000,000		800,000,000
Secured Debt \| 2016 Credit Facility Agreement
Debt Instrument [Line Items]
Line of credit facility, frequency of payments in quarterly installments \| installment	16
Secured Debt \| Term loan \| 2016 Credit Facility Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			1,500,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross			595,000,000		$ 155,000,000
Revolving Credit Facility \| 2016 Credit Facility Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			1,200,000,000
CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 2,800,000,000
CEB \| 2016 Credit Facility Agreement
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 1,675,000,000
CEB \| Senior notes
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 800,000,000
CEB \| Secured Debt \| Term B facility \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%
CEB \| Secured Debt \| Term B facility \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
CEB \| Secured Debt \| Term loan \| 2016 Credit Facility Agreement
Debt Instrument [Line Items]
Additional borrowing capacity	$ 900,000,000
CEB \| Secured Debt \| Term B facility \| 2016 Credit Facility Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 500,000,000
Proceeds from issuance of debt	500,000,000
CEB \| Revolving Credit Facility
Debt Instrument [Line Items]
Proceeds from issuance of debt	275,000,000
Bridge Loan \| CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 300,000,000
Debt instrument term	364 days		364 days

Debt - Bridge Facility and Senior Notes (Details) - USD ($) $ in Millions			12 Months Ended
	Apr. 05, 2017	Mar. 30, 2017	Dec. 31, 2017
Senior notes
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 800.0
CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 2,800.0
CEB \| Senior notes
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 800.0
Debt instrument, fixed interest rate		5.125%
Issue price, percent		100.00%
Redeemable percentage of principal amount		40.00%
CEB \| Senior notes \| Redemption period one
Debt Instrument [Line Items]
Redemption price percentage		105.125%
CEB \| Senior notes \| Redemption period two
Debt Instrument [Line Items]
Redemption price percentage		100.00%
CEB \| Senior notes \| Redemption period three
Debt Instrument [Line Items]
Redemption price percentage		101.00%
Bridge Loan \| CEB
Debt Instrument [Line Items]
Debt instrument term	364 days		364 days
Proceeds from issuance of debt	$ 300.0
Repayments of short-term debt			$ 300.0

Debt - Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,312,092	$ 3,323,062
Less: deferred financing fees	(30,405)	(44,217)
Net balance sheet carrying amount	2,281,687	3,278,845
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	155,000	595,000
Term loan
Debt Instrument [Line Items]
Long-term debt, gross	1,355,062	1,429,312
Term B facility
Debt Instrument [Line Items]
Long-term debt, gross	0	496,250
Senior notes
Debt Instrument [Line Items]
Long-term debt, gross	800,000	800,000
Connecticut Economic Development Program
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,030	$ 2,500

Debt - Debt Outstanding Footnotes (Details) - USD ($) $ in Thousands			12 Months Ended
	Apr. 05, 2017	Mar. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2012
Debt Instrument [Line Items]
Debt instrument, interest rate at period end			4.17%
Long-term Debt, Fiscal Year Maturity [Abstract]
2019			$ 102,600
2020			139,700
2021			37,600
2022			1,230,000
Thereafter			800,000
Write off of deferred financing fees				$ 6,100
Payments of deferred financing fees			0	$ 51,171	$ 4,975
Senior notes
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 800,000
Connecticut Economic Development Program
Debt Instrument [Line Items]
Debt instrument, fixed interest rate						3.00%
Debt instrument term						10 years
Term B facility
Long-term Debt, Fiscal Year Maturity [Abstract]
Write off of deferred financing fees			$ 6,900
CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 2,800,000
CEB \| Senior notes
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 800,000
Debt instrument, fixed interest rate		5.125%
Revolving Credit Facility
Debt Instrument [Line Items]
Interest rate at period end			4.02%
Floating eurodollar base rate			2.52%
Additional interest above base rate			1.50%
Line of credit facility, remaining borrowing capacity			$ 1,000,000
Revolving Credit Facility \| CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 275,000

Debt - Interest Rate Swaps (Details) $ in Thousands	12 Months Ended
Debt - Interest Rate Swaps (Details) $ in Thousands	Dec. 31, 2017 USD ($) outstanding_contract	Dec. 31, 2018 USD ($) derivative_instrument outstanding_contract	Dec. 31, 2016 USD ($)
Derivative [Line Items]
Number of Contracts \| outstanding_contract	142	142
Contract notional amount	$ 2,086,764	$ 3,027,375
Interest rate swap
Derivative [Line Items]
Number of Contracts \| derivative_instrument		5
Contract notional amount		$ 1,400,000
Derivative, term of contract	30 days
Interest rate derivative hedge, asset (liability), net	$ 10,700		$ (3,400)
Forward starting interest rate swap
Derivative [Line Items]
Number of Contracts \| derivative_instrument		2
Contract notional amount		$ 700,000
Minimum \| Interest rate swap
Derivative [Line Items]
Derivative, fixed interest rate	1.53%
Maximum \| Interest rate swap
Derivative [Line Items]
Derivative, fixed interest rate	2.13%

Commitments and Contingencies - Future Minimum Annual Cash Payments Under Non-Cancelable Operating Lease Agreements (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 130,991
2020	121,802
2021	118,945
2022	111,117
2023	106,113
Thereafter	689,360
Total minimum lease payments	1,278,328
Sublease income	$ 372,000

Stockholders' Equity - Additional Information (Details) $ / shares in Units, shares in Millions		12 Months Ended
	Apr. 05, 2017 $ / shares shares	Dec. 31, 2018 USD ($) vote $ / shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)
Class of Stock [Line Items]
Common stock par value (in Dollars per share) \| $ / shares		$ 0.0005	$ 0.0005
Common stock, number of votes per share \| vote		1
Payments for purchases of treasury stock		$ 260,832,000	$ 41,272,000	$ 58,961,000
Share repurchase program, authorized amount		1,200,000,000
Stock repurchase program, remaining authorized repurchase amount		$ 900,000,000
CEB
Class of Stock [Line Items]
Business acquisition, shares issued as consideration \| shares	7.4
Business acquisition, consideration transferred, per share value (in dollars per share) \| $ / shares	$ 109.65

Stockholders' Equity - Summary of Transactions Relating to Common Stock (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock
Common Stock Outstanding Roll Forward [Roll Forward]
Beginning Balance	163,602,067	156,234,415	156,234,415
Issuances under stock plans	0	0	0
Issued in connection with the acquisition of CEB		7,367,652
Purchases for treasury	0	0	0
Ending Balance	163,602,067	163,602,067	156,234,415
Treasury Stock
Common Stock Outstanding Roll Forward [Roll Forward]
Beginning Balance	72,779,205	73,583,172	73,896,245
Issuances under stock plans	(933,246)	(1,186,150)	(923,696)
Issued in connection with the acquisition of CEB		0
Purchases for treasury	2,054,018	382,183	610,623
Ending Balance	73,899,977	72,779,205	73,583,172

Stockholders' Equity - Changes in AOCL/I by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	$ 983,465	$ 60,878	$ (132,400)
Other comprehensive income (loss) activity during the period:
Change in AOCI/L before reclassifications to income	19,619	45,871
Reclassifications from AOCI/L to income	(61,585)	5,320
Other comprehensive (loss) income, net of tax	(41,966)	51,191	(5,281)
Ending Balance	850,757	983,465	60,878
AOCI Attributable to Parent
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	1,508	(49,683)	(44,402)
Other comprehensive income (loss) activity during the period:
Other comprehensive (loss) income, net of tax	(41,966)	51,191	(5,281)
Ending Balance	(39,867)	1,508	(49,683)
Interest Rate Swaps
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	2,483	(1,409)
Other comprehensive income (loss) activity during the period:
Change in AOCI/L before reclassifications to income	(9,447)	(1,492)
Reclassifications from AOCI/L to income	(1,397)	5,384
Other comprehensive (loss) income, net of tax	(10,844)	3,892
Ending Balance	(7,770)	2,483	(1,409)
Defined Benefit Pension Plans
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(5,861)	(5,797)
Other comprehensive income (loss) activity during the period:
Change in AOCI/L before reclassifications to income	0	0
Reclassifications from AOCI/L to income	123	(64)
Other comprehensive (loss) income, net of tax	123	(64)
Ending Balance	(5,738)	(5,861)	(5,797)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	4,886	(42,477)
Other comprehensive income (loss) activity during the period:
Change in AOCI/L before reclassifications to income	29,066	47,363
Reclassifications from AOCI/L to income	(60,311)	0
Other comprehensive (loss) income, net of tax	(31,245)	47,363
Ending Balance	$ (26,359)	4,886	$ (42,477)
ASU 2018-02 \| AOCI Attributable to Parent
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Adoption of ASU		591
ASU 2018-02 \| Interest Rate Swaps
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Adoption of ASU		$ 591

Stock-Based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	4,900,000
Common stock par value (in Dollars per share)	$ 0.0005	$ 0.0005
Stock-based compensation expense	$ 66,172,000	$ 78,943,000	$ 46,661,000
Total share-based compensation cost not yet recognized	$ 79,100,000
Remaining weighted average service period	2 years 4 months 1 day
Weighted average remaining contractual term	1 year 1 month
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, stock purchases as a percentage of employee compensation, maximum	10.00%
Maximum share value authorized for purchase under employee stock purchase plan	$ 23,750
Exercisable price percentage of closing price of another class of stock	95.00%
Maximum number of shares that may be purchased by eligible participants	700,000
Proceeds from stock grants	$ 14,700,000	11,700,000	9,300,000
Retirement Eligible Employees Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 19,400,000	$ 22,900,000	$ 19,400,000
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average service period	6 years 1 month 10 days
Award vesting period	4 years
Award expiry period from date of grant	7 years
Total compensation cost not yet recognized, period for recognition	4 years
Equity instruments number of shares unvested (in shares)	1,200,000	1,200,000
Aggregate intrinsic value of outstanding shares	$ 46,000,000
Aggregate intrinsic value of shares vested and exercisable	$ 26,900,000
Grants during period (in shares)	300,000
Stock appreciation rights \| Unvested
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments number of shares unvested (in shares)	700,000
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments number of shares unvested (in shares)	1,400,000	1,500,000
Grants during period (in shares)	700,000
Restricted stock units \| Service-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Grants during period (in shares)	400,000
Restricted stock units \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants during period (in shares)	300,000	200,000
Performance share, actual yielded performance, percent	144.00%
Restricted stock units \| Performance Shares \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance shares, target performance percentage	0.00%
Restricted stock units \| Performance Shares \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance shares, target performance percentage	200.00%
CSEs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments number of shares unvested (in shares)	109,780	110,013
Grants during period (in shares)	5,550
Base fee percentage	50.00%

Stock-Based Compensation - Stock-Based Compensation Expense By Award Type (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 66.2	$ 78.9	$ 46.7
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	6.3	5.6	5.6
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	59.2	72.6	40.4
Common stock equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0.7	$ 0.7	$ 0.7

Stock-Based Compensation - Stock-Based Compensation Expense Recognized In Consolidated Statements Of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 66.2	$ 78.9	$ 46.7
Cost of services and product development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	28.1	25.8	21.9
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	36.2	35.5	24.8
Acquisition and integration charges
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1.9	$ 17.6	$ 0.0

Stock-Based Compensation - Summary Of Changes In SARs Outstanding (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Weighted Average Remaining Contractual Term (Years)
Remaining weighted average service period	2 years 4 months 1 day
Stock appreciation rights
SARs
Outstanding, Beginning Balance (in shares)	1.2
Granted (in shares)	0.3
Exercised (in shares)	(0.3)
Outstanding, Ending Balance (in shares)	1.2	1.2
Vested and exercisable, ending balance (in shares)	0.5
Per Share Weighted Average Exercise Price
Outstanding, Beginning Balance (in Dollars per share)	$ 76.73
Granted (in Dollars per share)	114.26
Exercised (in Dollars per share)	60.67
Outstanding, Ending Balance (in Dollars per share)	89.45	$ 76.73
Vested and exercisable, ending balance (in Dollars per share)	75.73
Per Share Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance (in Dollars per share)	17.35
Granted (in Dollars per share)	25.63
Exercised (in Dollars per share)	15.10
Outstanding, Ending Balance (in Dollars per share)	19.88	$ 17.35
Vested and exercisable, ending balance (in Dollars per share)	$ 17.02
Weighted Average Remaining Contractual Term (Years)
Weighted average remaining contractual terms	4 years 4 months	4 years 3 months 10 days
Remaining weighted average service period	6 years 1 month 10 days
Weighted average remaining contractual terms vested and exercisable	3 years 2 months 25 days

Stock-Based Compensation - Weighted-Average Assumptions Used To Determine Fair Value Of SARs Grants On Date Of Grant Using Black-Scholes-Merton Valuation Model (Details) - Stock appreciation rights	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected stock price volatility	21.00%	22.00%	22.00%
Risk-free interest rate	2.50%	1.80%	1.10%
Expected life in years	4 years 6 months 8 days	4 years 6 months 11 days	4 years 4 months 21 days

Stock-Based Compensation - Summary Of Changes In RSUs Outstanding (Details) - Restricted stock units shares in Millions	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Restricted Stock Units (RSUs)
Outstanding, Beginning Balance (in shares) \| shares	1.5
Granted (in shares) \| shares	0.7
Vested and released (in shares) \| shares	(0.7)
Forfeited (in shares) \| shares	(0.1)
Outstanding, Ending Balance (in shares) \| shares	1.4
Per Share Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance (in Dollars per share) \| $ / shares	$ 91.47
Granted (in Dollars per share) \| $ / shares	112.96
Vested and released (in Dollars per share) \| $ / shares	88.69
Forfeited (in Dollars per share) \| $ / shares	104.95
Outstanding, Ending Balance (in Dollars per share) \| $ / shares	$ 101.75

Stock-Based Compensation - Summary Of Changes In CSEs Outstanding (Details) - CSEs	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Common Stock Equivalents (CSEs)
Outstanding, Beginning Balance (in shares) \| shares	110,013
Granted (in shares) \| shares	5,550
Converted to shares of Common Stock upon grant (in shares) \| shares	(5,783)
Outstanding, Ending Balance (in shares) \| shares	109,780
Per Share Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance (in Dollars per share) \| $ / shares	$ 23.19
Granted (in Dollars per share) \| $ / shares	131.49
Converted to shares of Common Stock upon grant (in Dollars per share) \| $ / shares	93.45
Outstanding, Ending Balance (in Dollars per share) \| $ / shares	$ 24.96

Computation of Earnings Per Share - Calculations Of Basic And Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 122,456	$ 3,279	$ 193,582
Denominator:
Weighted average common shares used in the calculation of basic earnings per share	90,827	88,466	82,571
Common share equivalents associated with stock-based compensation plans	1,295	1,324	1,249
Shares used in the calculation of diluted earnings per share	92,122	89,790	83,820
Earnings per share:
Basic (in dollars per share)	$ 1.35	$ 0.04	$ 2.34
Diluted (in dollars per share)	$ 1.33	$ 0.04	$ 2.31

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Computation of Earnings Per Share - Additional Information (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Tax act, income tax benefit (in dollars per share)		$ 0.66
Common Stock Equivalents (CSEs)
Class of Stock [Line Items]
Stock repurchased during period (in shares)	2.1	0.4	0.6

Computation of Earnings Per Share - Common Share Equivalents Not Included in the Computation of Diluted EPS (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Anti-dilutive common share equivalents as of December 31 (in shares)	0.0	0.3	0.2
Average market price per share of Common Stock during the year (in dollars per share)	$ 135.60	$ 116.09	$ 92.58

Income Taxes - Summary of Components of Income Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
U.S.	$ 34,159	$ (135,757)	$ 182,178
Non-U.S.	146,962	7,940	106,253
Income (loss) before income taxes	$ 181,121	$ (127,817)	$ 288,431

Income Taxes - Components of Income Tax Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current tax expense:
U.S. federal	$ 2,817	$ 48,339	$ 58,616
State and local	6,969	434	11,292
Foreign	45,042	38,602	27,536
Total current	54,828	87,375	97,444
Deferred tax (benefit) expense:
U.S. federal	12,462	(176,046)	(61)
State and local	1,258	(14,363)	(349)
Foreign	(13,795)	(25,898)	(1,626)
Total deferred	(75)	(216,307)	(2,036)
Total current and deferred	54,753	(128,932)	95,408
Total tax expense (benefit)	58,665	(131,096)	94,849
Benefit (expense) relating to interest rate swaps used to increase (decrease) equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	3,840	(2,477)	(1,113)
Benefit from stock transactions with employees used to increase equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	58	46	52
Benefit relating to defined-benefit pension adjustments used to increase equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	$ 14	$ 267	$ 502

Income Taxes - Current and Long-Term Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accrued liabilities	$ 96,292	$ 80,557
Loss and credit carryforwards	14,830	59,502
Assets relating to equity compensation	19,653	24,874
Other assets	14,092	30,236
Gross deferred tax assets	144,867	195,169
Property, equipment, and leasehold improvements	(3,421)	(962)
Intangible assets	(214,580)	(372,542)
Prepaid expenses	(41,926)	(35,126)
Other liabilities	(61,068)	(6,584)
Gross deferred tax liabilities	(320,995)	(415,214)
Valuation allowance	(4,066)	(3,192)
Net deferred tax liabilities	$ (180,194)	$ (223,237)

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Line Items]
Non-current deferred tax assets	$ 34,494	$ 31,067
Non-current deferred tax liabilities	214,687	206,338
Valuation allowance	4,066	3,192
Tax act, provisional tax expense	13,800	123,200
Tax act, provisional amount of one-time transition tax liability	8,400	63,600
Tax act, remaining tax liability for one time transition tax	10,000
Unrecognized tax benefits	90,349	60,269	$ 37,099
Unrecognized tax benefits reductions resulting from settlements with taxing authorities and lapse of applicable statute of limitations	20,000
Unrecognized tax benefits that would impact effective tax rate	86,200
Unrecognized tax benefits that would result adjustments to other tax accounts	4,100
Income tax penalties and interest expense	6,700	6,400
Income tax examination, penalties and interest expense	700	900
Accumulated undistributed earnings of non-US subsidiaries	171,000
State and local jurisdiction
Income Tax [Line Items]
Operating loss carryforwards	35,200
Tax credit carryforwards	$ 2,200
State and local jurisdiction \| Minimum
Income Tax [Line Items]
Tax credit carryforwards, expiration period	5 years
State and local jurisdiction \| Maximum
Income Tax [Line Items]
Tax credit carryforwards, expiration period	6 years
State and local jurisdiction \| Expire within one to five years
Income Tax [Line Items]
Operating loss carryforwards	$ 100
State and local jurisdiction \| Expire within one to five years \| Minimum
Income Tax [Line Items]
Operating loss carryforwards expiration period	1 year
State and local jurisdiction \| Expire within one to five years \| Maximum
Income Tax [Line Items]
Operating loss carryforwards expiration period	5 years
State and local jurisdiction \| Expire within six to fifteen years
Income Tax [Line Items]
Operating loss carryforwards	$ 3,500
State and local jurisdiction \| Expire within six to fifteen years \| Minimum
Income Tax [Line Items]
Operating loss carryforwards expiration period	6 years
State and local jurisdiction \| Expire within six to fifteen years \| Maximum
Income Tax [Line Items]
Operating loss carryforwards expiration period	15 years
State and local jurisdiction \| Expire within sixteen to twenty years
Income Tax [Line Items]
Operating loss carryforwards	$ 31,600
State and local jurisdiction \| Expire within sixteen to twenty years \| Minimum
Income Tax [Line Items]
Operating loss carryforwards expiration period	16 years
State and local jurisdiction \| Expire within sixteen to twenty years \| Maximum
Income Tax [Line Items]
Operating loss carryforwards expiration period	20 days
Foreign Tax Authority
Income Tax [Line Items]
Operating loss carryforwards	$ 5,000
Foreign Tax Authority \| Expire over next twenty years
Income Tax [Line Items]
Operating loss carryforwards	$ 100
Operating loss carryforwards expiration period	20 years
Foreign Tax Authority \| Carried forward indefinitely
Income Tax [Line Items]
Operating loss carryforwards	$ 4,900
Other liabilities
Income Tax [Line Items]
Non-current deferred tax assets	34,500	30,500
Other liabilities
Income Tax [Line Items]
Non-current deferred tax liabilities	$ 214,700	$ 253,700

Income Taxes - Differences Between U.S. Federal Statutory Income Tax Rate and Effective Tax Rate on Income Before Income Taxes (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory tax rate	21.00%	35.00%	35.00%
State income taxes, net of federal benefit	0.00%	3.60%	2.30%
Effect of non-U.S. operations	(10.60%)	5.90%	(6.10%)
Change in the reserve for tax contingencies	15.70%	(2.80%)	3.20%
Law changes	(1.30%)	41.80%	0.00%
Stock-based compensation expense	(5.30%)	11.00%	(3.80%)
Nondeductible acquisition costs	0.90%	(7.90%)	2.60%
Nondeductible meals and entertainment costs	2.70%	(3.50%)	1.10%
Gains/Losses on divested operations and held-for-sale assets	12.20%	13.10%	0.00%
Limitation on executive compensation	2.70%	(0.10%)	0.00%
Foreign-derived intangible income	(2.00%)	0.00%	0.00%
Change in the valuation allowance	0.50%	3.00%	(0.20%)
Goodwill	(3.80%)	(0.00%)	(0.00%)
Other items, net	(0.30%)	3.50%	(1.20%)
Effective tax rate	32.40%	102.60%	32.90%

Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits, Excluding Interest and Penalties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 60,269	$ 37,099
Additions based on tax positions related to the current year	27,371	10,883
Additions for tax positions of prior years	14,691	24,299
Reductions for tax positions of prior years	(3,939)	(10,613)
Reductions for expiration of statutes	(6,293)	(1,368)
Settlements	(472)	(1,769)
Decrease in foreign currency exchange rates	(1,278)
Increase in foreign currency exchange rates		1,738
Ending balance	$ 90,349	$ 60,269

Derivatives and Hedging - Outstanding Derivatives Contracts (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) derivative_instrument outstanding_contract	Dec. 31, 2017 USD ($) outstanding_contract
Derivatives, Fair Value [Line Items]
Number of Contracts \| outstanding_contract	142	142
Notional Amounts	$ 3,027,375	$ 2,086,764
Fair Value Asset (Liability), Net	(12,623)	3,860
Unrealized Gain (Loss) Recorded in AOCI/L	$ (7,770)	$ 2,483
Interest rate swaps
Derivatives, Fair Value [Line Items]
Number of Contracts \| derivative_instrument	5
Notional Amounts	$ 1,400,000
Other liabilities \| Interest rate swaps \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Number of Contracts \| outstanding_contract	7
Notional Amounts	$ 2,100,000
Fair Value Asset (Liability), Net	(10,681)
Unrealized Gain (Loss) Recorded in AOCI/L	$ (7,770)
Other liabilities \| Interest rate swaps \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Number of Contracts \| outstanding_contract		5
Notional Amounts		$ 1,400,000
Fair Value Asset (Liability), Net		3,412
Unrealized Gain (Loss) Recorded in AOCI/L		$ 2,483
Accrued liabilities \| Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Contracts \| outstanding_contract	135
Notional Amounts	$ 927,375
Fair Value Asset (Liability), Net	(1,942)
Unrealized Gain (Loss) Recorded in AOCI/L	$ 0
Other current assets \| Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Contracts \| outstanding_contract		137
Notional Amounts		$ 686,764
Fair Value Asset (Liability), Net		448
Unrealized Gain (Loss) Recorded in AOCI/L		$ 0

Derivatives and Hedging - Derivative Gains And Losses That Have Been Recognized In Condensed Consolidated Statements Of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 8.5	$ 7.1	$ 7.9
Interest (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	(1.9)	7.9	7.6
Other expense (income), net
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 10.4	$ (0.8)	$ 0.3

Fair Value Disclosures - Assets And Liabilities Measured At Fair Value On Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets:
Total Assets	$ 67,964	$ 93,590
Level 1
Assets:
Total Assets	8,956	29,108
Level 1 \| Plan Assets
Assets:
Total Assets	8,956	29,108
Level 2
Assets:
Total Assets	59,008	64,482
Liabilities:
Total Liabilities	858,671	929,065
Level 2 \| Foreign currency forward contracts
Assets:
Total Assets	1,318	2,053
Liabilities:
Total Liabilities	3,260	1,605
Level 2 \| Interest rate swap contracts
Assets:
Total Assets	0	3,412
Liabilities:
Total Liabilities	10,681	0
Level 2 \| Plan Assets
Assets:
Total Assets	57,690	59,017
Level 2 \| Plan Liabilities
Liabilities:
Total Liabilities	68,570	89,900
Level 2 \| Debt \| Senior notes
Liabilities:
Total Liabilities	$ 776,160	$ 837,560

Fair Value Disclosures - Additional Information (Details) - USD ($) $ in Millions	Mar. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds at carrying value		$ 9.0	$ 29.1
Cash surrender value of life insurance		$ 57.7	$ 59.0
Senior notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from issuance of debt	$ 800.0

Employee Benefits - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percent	4.00%
Maximum annual contribution per employee, amount	$ 7,200
Defined contribution plan cost recognized	36,700,000	$ 29,800,000	$ 22,900,000
Compensation expense related to deferred compensation plan	1,700,000	400,000	$ 100,000
Expected future benefit payments, in 2019	1,200,000
Expected future benefit payments, in 2020	1,500,000
Expected future benefit payments, in 2021	1,600,000
Expected future benefit payments, in 2022	1,700,000
Expected future benefit payments, in 2023	2,100,000
Expected future benefit payments in the five years thereafter	$ 12,100,000
Expected long-term return on assets	2.45%
Contributions by employer	$ 3,000,000
Benefits paid to participants under defined benefit plans	$ 1,400,000
Weighted average amortization period	13 years
Future amortization of unrecognized gains losses	$ 200,000
Other assets	9,000,000	9,100,000
Other liabilities
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation plan assets	66,600,000	88,100,000
Other liabilities
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation liability	$ 68,600,000	$ 89,900,000

Employee Benefits - Components of Net Periodic Pension Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 3,145	$ 2,820	$ 2,780
Interest cost	840	765	850
Expected return on plan assets	(475)	(360)	(375)
Recognition of actuarial loss	340	350	200
Total defined benefit pension expense	$ 3,850	$ 3,575	$ 3,455

Employee Benefits - Assumptions Used in Computation of Net Periodic Pension Expense (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Weighted-average discount rate	1.81%	1.78%	1.78%
Average compensation increase	2.58%	2.66%	2.67%

Employee Benefits - Information Related to Changes in Projected Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year	$ 45,450	$ 38,400	$ 35,870
Service cost	3,145	2,820	2,780
Interest cost	840	765	850
Actuarial loss (gain) due to assumption changes and plan experience	(430)	690	1,480
Additions and contractual termination benefits	(950)	(860)	0
Benefits paid	(1,400)	(920)	(1,640)
Foreign currency impact	(1,765)	4,555	(940)
Projected benefit obligation at end of year	$ 44,890	$ 45,450	$ 38,400

Employee Benefits - Benefit Plans and Related Amounts Recorded in Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligation	$ 44,890	$ 45,450	$ 38,400	$ 35,870
Pension plan assets at fair value	(19,460)	(18,475)	(14,465)
Funded status – shortfall	25,430	26,975	23,935
Amounts recorded in the Consolidated Balance Sheets for the plans:
Other liabilities — accrued pension obligation	25,430	26,975	23,935
Stockholders’ equity — deferred actuarial loss	$ (5,738)	$ (5,861)	$ (5,797)

Segment Information - Additional Information (Details)	12 Months Ended
Segment Information - Additional Information (Details)	Dec. 31, 2018 segment
Segment Reporting Information [Line Items]
Number of reportable segments	3
Maximum
Segment Reporting Information [Line Items]
Percent of target bonus charges allocated to segments	100.00%

Segment Information - Information About Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating income (loss)	$ 259,715	$ (6,329)	$ 305,141
Operating Segments
Segment Reporting Information [Line Items]
Revenues	3,975,454	3,311,494	2,444,540
Total segment gross contribution	2,518,973	2,000,386	1,512,000
Operating Segments \| Research
Segment Reporting Information [Line Items]
Revenues	3,105,764	2,471,280	1,857,001
Total segment gross contribution	2,144,097	1,653,014	1,285,611
Operating Segments \| Conferences
Segment Reporting Information [Line Items]
Revenues	410,461	337,903	268,605
Total segment gross contribution	207,260	163,480	136,655
Operating Segments \| Consulting
Segment Reporting Information [Line Items]
Revenues	353,667	327,661	318,934
Total segment gross contribution	102,541	93,643	89,734
Operating Segments \| Other
Segment Reporting Information [Line Items]
Revenues	105,562	174,650	0
Total segment gross contribution	65,075	90,249	0
Corporate and Reconciling Items
Segment Reporting Information [Line Items]
Corporate and other expenses	$ (2,259,258)	$ (2,006,715)	$ (1,206,859)

Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Costs and expenses:
Cost of services and product development	$ 1,468,800	$ 1,320,198	$ 945,648
Selling, general and administrative	1,884,141	1,599,004	1,089,184
Acquisition and integration charges	107,197	158,450	42,598
Operating income (loss)	259,715	(6,329)	305,141
Interest expense and other, net	124,041	121,488	16,710
Gain from divested operations	45,447	0	0
Provision (benefit) for income taxes	58,665	(131,096)	94,849
Net income	122,456	3,279	193,582
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	2,518,973	2,000,386	1,512,000
Corporate and Reconciling Items
Costs and expenses:
Cost of services and product development	12,319	9,090	13,108
Selling, general and administrative	1,884,141	1,599,004	1,089,184
Depreciation and amortization	255,601	240,171	61,969
Acquisition and integration charges	$ 107,197	$ 158,450	$ 42,598

Segment Information - Summarized Information by Geographic Location (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Long-lived assets:
Long-lived assets	$ 424,034	$ 415,249	$ 210,877
United States and Canada
Long-lived assets:
Long-lived assets	305,928	288,735	143,921
Europe, Middle East and Africa
Long-lived assets:
Long-lived assets	67,306	84,840	42,326
Other International
Long-lived assets:
Long-lived assets	$ 50,800	$ 41,674	$ 24,630

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(11))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(15))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(13))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(16))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(14))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(10))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Valuation and Qualifying Accounts - Summarized Activity in Allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 12,700	$ 7,400	$ 6,900
Additions Charged to Expense	12,500	16,600	4,750
Additions Charged Against Revenues	0	5,500	4,850
Deductions from Reserve	(11,300)	(16,800)	(9,100)
Reclassification to Accounts Payable and Accrued Liabilities	(6,200)
Balance at End of Year	$ 7,700	$ 12,700	$ 7,400