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Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
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
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		90,833,817
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 10,832,607,830

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 538,908	$ 474,233
Fees receivable, net of allowances of $12,700 and $7,400 respectively	1,176,843	643,013
Deferred commissions	205,260	141,410
Prepaid expenses and other current assets	124,632	84,540
Assets held-for-sale	542,965	0
Total current assets	2,588,608	1,343,196
Property, equipment and leasehold improvements, net	221,507	121,606
Goodwill	2,987,294	738,453
Intangible assets, net	1,292,022	76,801
Other assets	193,742	87,279
Total Assets	7,283,173	2,367,335
Current liabilities:
Accounts payable and accrued liabilities	666,821	440,771
Deferred revenues	1,630,198	989,478
Current portion of long-term debt	379,721	30,000
Liabilities held-for-sale	145,845	0
Total current liabilities	2,822,585	1,460,249
Long-term debt, net of deferred financing fees	2,899,124	664,391
Other liabilities	577,999	181,817
Total Liabilities	6,299,708	2,306,457
Preferred stock:
$.01 par value, authorized 5,000,000 shares; none issued or outstanding	0	0
Common stock:
$.0005 par value, authorized 250,000,000 shares for both periods; 163,602,067 shares issued at December 31, 2017 and 156,234,415 shares issued at December 31, 2016	82	78
Additional paid-in capital	1,761,383	863,127
Accumulated other comprehensive income (loss), net	1,508	(49,683)
Accumulated earnings	1,647,284	1,644,005
Treasury stock, at cost, 72,779,205 and 73,583,172 common shares, respectively	(2,426,792)	(2,396,649)
Total Stockholders’ Equity	983,465	60,878
Total Liabilities and Stockholders’ Equity	$ 7,283,173	$ 2,367,335

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fees receivable, allowances	$ 12,700	$ 7,400
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	72,779,205	73,583,172

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Research	$ 2,471,280	$ 1,857,001	$ 1,614,904
Consulting	327,661	318,934	296,317
Events	337,903	268,605	251,835
Talent Assessment & Other	174,650	0	0
Total revenues	3,311,494	2,444,540	2,163,056
Costs and expenses:
Cost of services and product development	1,320,198	945,648	839,076
Selling, general and administrative	1,599,004	1,089,184	962,677
Depreciation	63,897	37,172	33,789
Amortization of intangibles	176,274	24,797	13,342
Acquisition and integration charges	158,450	42,598	26,175
Total costs and expenses	3,317,823	2,139,399	1,875,059
Operating (loss) income	(6,329)	305,141	287,997
Interest income	3,011	2,449	1,766
Interest expense	(127,947)	(27,565)	(22,548)
Other income, net	3,448	8,406	4,996
(Loss) income before income taxes	(127,817)	288,431	272,211
(Benefit) provision for income taxes	(131,096)	94,849	96,576
Net income	$ 3,279	$ 193,582	$ 175,635
Net income per share:
Basic (in Dollars per share)	$ 0.04	$ 2.34	$ 2.09
Diluted (in Dollars per share)	$ 0.04	$ 2.31	$ 2.06
Weighted average shares outstanding:
Basic (in shares)	88,466	82,571	83,852
Diluted (in shares)	89,790	83,820	85,056

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 3,279	$ 193,582	$ 175,635
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	47,363	(5,986)	(23,089)
Interest rate hedges - net change in deferred gain or loss	3,892	1,670	(1,339)
Pension plans - net change in deferred actuarial loss	(64)	(965)	1,196
Other comprehensive income (loss), net of tax	51,191	(5,281)	(23,232)
Comprehensive income	$ 54,470	$ 188,301	$ 152,403

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss), Net	Accumulated Earnings	Treasury Stock
Beginning Balance at Dec. 31, 2014	$ 161,171	$ 78	$ 764,433	$ (21,170)	$ 1,275,049	$ (1,857,219)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	175,635				175,635
Other comprehensive income (loss)	(23,232)			(23,232)
Issuances under stock plans	7,531		(5,964)			13,495
Stock compensation tax benefits	13,928		13,928
Common share repurchases	(513,582)					(513,582)
Stock compensation expense	46,149		46,149
Ending 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]
Adoption of ASU No. 2016-09	(261)				(261)
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 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 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)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 3,279	$ 193,582	$ 175,635
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	240,171	61,969	47,131
Stock-based compensation expense	78,943	46,661	46,149
Excess tax benefits from stock-based compensation exercises	0	0	(13,860)
Deferred taxes	(217,414)	(2,648)	344
Gain on extinguishment of debt	0	(2,500)	0
Amortization and write-off of deferred financing fees	15,062	3,082	1,512
Changes in assets and liabilities, net of acquisitions:
Fees receivable, net	(368,516)	(68,661)	(44,476)
Deferred commissions	(61,393)	(18,673)	(13,236)
Prepaid expenses and other current assets	13,251	(21,604)	(13,268)
Other assets	(18,529)	20,005	(14,733)
Deferred revenues	382,852	97,979	91,840
Accounts payable, accrued, and other liabilities	186,811	56,440	82,523
Cash provided by operating activities	254,517	365,632	345,561
Investing activities:
Additions to property, equipment and leasehold improvements	(110,765)	(49,863)	(46,128)
Acquisitions - cash paid (net of cash acquired)	(2,634,809)	(34,186)	(196,229)
Cash used in investing activities	(2,745,574)	(84,049)	(242,357)
Financing activities:
Proceeds from employee stock purchase plan	11,711	9,250	7,499
Proceeds from borrowings	3,025,000	715,000	440,000
Payments for deferred financing fees	(51,171)	(4,975)	0
Payments on borrowings	(404,438)	(835,000)	(20,000)
Purchases of treasury stock	(41,272)	(58,961)	(509,049)
Excess tax benefits from stock-based compensation exercises	0	0	13,860
Net Cash Provided by (Used in) Financing Activities	2,539,830	(174,686)	(67,690)
Net increase in cash and cash equivalents	48,773	106,897	35,514
Effects of exchange rates on cash and cash equivalents	25,902	(5,640)	(27,840)
Cash and cash equivalents, beginning of period	474,233	372,976	365,302
Cash and cash equivalents, end of period	548,900	474,233	372,976
Cash paid during the period for:
Interest	98,500	23,400	21,200
Income taxes, net of refunds received	$ 76,100	$ 86,300	$ 83,500

Business and Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

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 mission-critical priorities 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 trusted as an objective resource and critical partner by more than 12,000 organizations in more than 100 countries — across all major functions, in every industry and enterprise size. To learn more about how we help decision makers fuel the future of business, visit gartner.com.

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 & 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 2017, 2016 and 2015 herein refer to the fiscal year unless otherwise indicated.

Gartner delivers its principal products and services globally through four business segments: Research, Consulting, Events and Talent Assessment & Other. The Company acquired two businesses during 2017, L2, Inc. ("L2") and CEB Inc. ("CEB"). Note 2 — Acquisitions and Divestiture provides additional information regarding these acquisitions. When used in these notes, the terms “Gartner,” “Company,” “we,” “us,” or “our” refer to Gartner, Inc. and its consolidated subsidiaries.

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, 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 completed acquisitions in each of the three years ended December 31, 2017 and detailed information related to these acquisitions is included in Note 2 — Acquisitions and Divestiture. The Company accounts for acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic No. 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 intangibles also requires management judgment and the evaluation of a number of factors, among them projected cash flows and the likelihood of competition.

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 $158.5 million, $42.6 million and $26.2 million of such charges in 2017, 2016 and 2015, respectively. Included in these directly-related and incremental charges are legal, consulting, retention, severance, and accruals for cash payments subject to the continuing employment of certain key employees of the acquired companies.

Revenue Recognition. Revenue is recognized in accordance with U.S. GAAP and SEC Staff Accounting Bulletin No. 104, Revenue Recognition (“SAB 104”). Revenues are only recognized once all required criteria for recognition have been met. 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.

On January 1, 2018, the Company adopted FASB Accounting Standards Update ("ASU") No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09") which requires changes in revenue recognition policies as well as enhanced disclosures. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. Additional information regarding the Company's adoption of ASU No. 2014-09 is provided below in the section titled Accounting standards issued but not yet adopted.

The Company’s revenues by significant source are as follows:

Research

Research revenues are mainly derived from subscription contracts for research products. The related revenues are deferred and recognized ratably over the applicable contract term. Fees derived from assisting organizations in selecting the right business software for their needs are recognized as earned when the leads are provided to vendors.

The Company typically enters into subscription contracts for research products for twelve-month periods or longer. The majority of research contracts are billable upon signing, absent special terms granted on a limited basis from time to time. Research contracts are 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 the contract that is billable as a fee receivable at the time the contract is signed with a corresponding amount as deferred revenue, since the contract represents a legally enforceable claim.

Consulting

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 on a proportional performance basis, while revenues from time and material engagements are recognized as work is delivered and/or services are provided. Revenues related to contract optimization engagements are contingent in nature and are only recognized upon satisfaction of all conditions related to their payment. Unbilled fees receivable associated with consulting engagements were $66.2 million at December 31, 2017 and $45.7 million at December 31, 2016.

Events

Events revenues are deferred and recognized upon the completion of the related symposium, conference or exhibition. In addition, the Company defers certain costs directly related to events and expenses these costs in the period during which the related symposium, conference or exhibition occurs. The Company's policy is to defer only those costs, primarily prepaid site and production services costs, which are incremental and are directly attributable to a specific event. Other costs of organizing and producing our events, primarily Company personnel and non-event specific expenses, are expensed in the period incurred. At the end of each fiscal quarter, the Company assesses on an event-by-event basis whether the expected direct costs of producing a scheduled event will exceed the expected revenues. If such costs are expected to exceed revenues, the Company records the expected loss in the period determined.

Talent Assessment & Other

Talent Assessment & Other revenues arising from knowledge and skill assessment services are recognized depending on the nature of the underlying contract: (i) ratably over the term of the service period; (ii) upon delivery; or (iii) on a proportional performance basis. Revenues from training programs and survey and questionnaire products are primarily recognized upon delivery of the service.

Allowance for losses. The Company maintains an allowance for losses which is composed of a bad debt allowance and a sales reserve. Provisions are charged against earnings, either as a reduction in revenues or an increase to expense. The determination of the allowance for losses 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.

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 the period in which the related revenues are earned. Commission expense is included in SG&A in the Consolidated Statements of Operations.

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 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 2017, 2016 and 2015, the Company recognized $78.9 million, $46.7 million and $46.1 million, respectively, of stock-based compensation expense.

Effective January 1, 2016, the Company adopted FASB ASU No. 2016-09, "Improvements to Employee Share-Based Payment Accounting" ("ASU No. 2016-09"). ASU No. 2016-09 mandated certain changes in accounting for stock-based compensation, including a requirement that excess tax benefits or deficiencies resulting from stock-based compensation awards be recognized in income tax expense or benefit subsequent to the date of adopting the new accounting standard. Previously, an entity’s excess tax benefits or deficiencies were recorded in additional paid-in capital. ASU No. 2016-09 also requires that excess tax benefits related to stock-based compensation awards be reported as an operating activity in an entity’s statement of cash flows. Previously, excess tax benefits were reported as financing activities. As permitted by ASU No. 2016-09, the Company elected to apply these changes prospectively, commencing on January 1, 2016. The provisions of ASU No. 2016-09 had no impact on our financial results for periods prior to 2016. If the Company had applied ASU No. 2016-09 to 2015: (i) income tax expense would have declined by $13.9 million; (ii) basic and diluted income per share would have increased by $0.17 and $0.16, respectively; and (iii) cash provided by operating activities would have increased by $13.9 million.

ASU No. 2016-09 also 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 optionally 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 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 within our consolidated balance sheets. In assessing the realizability of deferred tax assets, management considers if it is more likely than not that some or all of the deferred tax assets will not be realized. We consider the availability of loss carryforwards, projected reversal of deferred tax liabilities, projected future taxable income, and ongoing prudent and feasible tax planning strategies in making this assessment. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not 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. As of December 31, 2017, the Company had $538.9 million of cash and cash equivalents and an additional $10.0 million of cash classified as held-for-sale in its Consolidated Balance Sheet, for a total cash balance of $548.9 million, which was reported as the ending cash balance in the Consolidated Statement of Cash Flows.

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. The cost of these operating leases, including any contractual rent increases, rent concessions, and landlord incentives, are recognized ratably over the life of the related lease agreement. Lease expense was $87.9 million, $38.0 million, and $33.8 million in 2017, 2016 and 2015, 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 lives of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful lives of the improvement or the remaining term of the related lease. The Company had total depreciation expense of $63.9 million, $37.2 million, and $33.8 million in 2017, 2016 and 2015, respectively. The Company's total fixed assets, less accumulated depreciation and amortization, consisted of the following (in thousands):



	Useful Life	December 31,
Category	(Years)	2017			2016
Computer equipment and software	2-7	$	189,015		$	166,385
Furniture and equipment	3-8	67,288			43,137
Leasehold improvements	2-15	175,716			96,603
		$	432,019		$	306,125
Less — accumulated depreciation and amortization		(210,512		)	(184,519		)
Property, equipment, and leasehold improvements, net		$	221,507		$	121,606

The Company incurs costs to develop internal use software used in our operations, and certain of these costs meeting the criteria outlined in FASB ASC Topic No. 350 are capitalized and amortized over future periods. Net capitalized development costs for internal use software was $26.9 million and $16.6 million at December 31, 2017 and 2016, respectively, which is included in the Computer equipment and software category above. Amortization of capitalized internal software development costs, which is classified in Depreciation in the Consolidated Statements of Operations, totaled $9.9 million, $8.8 million and $8.2 million during 2017, 2016 and 2015 respectively.

Finite-lived intangible assets. The Company has finite-lived intangible assets which are amortized against earnings using the straight-line method over their expected useful lives. Changes in intangible assets subject to amortization during the two-year period ended December 31, 2017 were as follows (in thousands):



December 31, 2017	Customer Relationships			Software			Content			Other			Total
Gross cost, December 31, 2016	$	63,369		$	16,025		$	3,728		$	33,645		$	116,767
Additions due to acquisitions (1)	1,253,312			180,787			141,707			24,384			1,600,190
Intangibles fully amortized	—			—			(4,227		)	—			(4,227		)
Reclassified as held-for-sale (2)	(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	1,200,316			123,424			104,313			54,929			1,482,982
Accumulated amortization (3)	(92,983		)	(26,344		)	(47,475		)	(24,158		)	(190,960		)
Balance, December 31, 2017	$	1,107,333		$	97,080		$	56,838		$	30,771		$	1,292,022



December 31, 2016	Customer Relationships			Software			Content			Other			Total
Gross cost, December 31, 2015	$	62,860		$	16,219		$	5,450		$	33,474		$	118,003
Additions due to acquisitions	3,677			—			1,948			302			5,927
Intangibles fully amortized	—			(125		)	(162		)	—			(287		)
Foreign currency translation impact	(3,168		)	(69		)	(3,508		)	(131		)	(6,876		)
Gross cost	63,369			16,025			3,728			33,645			116,767
Accumulated amortization (3)	(16,744		)	(8,904		)	(2,033		)	(12,285		)	(39,966		)
Balance, December 31, 2016	$	46,625		$	7,121		$	1,695		$	21,360		$	76,801


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


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


(3)	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.

Amortization expense related to finite-lived intangible assets was $176.3 million, $24.8 million and $13.3 million in 2017, 2016 and 2015, respectively. The estimated future amortization expense by year from finite-lived intangibles is as follows (in thousands):



2018	$	190,442
2019	134,530
2020	128,133
2021	107,715
2022 and thereafter	731,202
	$	1,292,022

Goodwill. Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair value 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 third quarter of 2017, which indicated no impairment of recorded goodwill, the Company utilized the qualitative 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 during the two-year period ended December 31, 2017 (in thousands):



	Research			Consulting			Events			Talent Assessment & Other			Total
Balance, December 31, 2015 (1)	$	575,292		$	98,412		$	41,655		$	—		$	715,359
Additions due to acquisitions	28,465			—			5,843			—			34,308
Foreign currency translation impact	(8,307		)	(1,932		)	(975		)	—			(11,214		)
Balance, December 31, 2016	$	595,450		$	96,480		$	46,523		$	—		$	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		)	1,318			483			20,530			4,044
Balance, December 31, 2017	$	2,619,677		$	97,798		$	187,920		$	81,899		$	2,987,294


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


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


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

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, 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 the carrying value can be recovered through undiscounted future operating cash flows. If events or circumstances indicate that the carrying value 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 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, 2017.

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 defined benefit plans in accordance with the requirements of FASB ASC Topic No. 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations. The Company recognized approximately $3.5 million of pension expense in each of the years ended 2017, 2016, and 2015. The Company classifies pension expense in SG&A in the Consolidated Statements of Operations.

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 in Interest expense in the Consolidated Statements of Operations. The Company amended its credit facility during 2017 and borrowed additional amounts related to its acquisitions. The Company had $3.3 billion of principal amount of debt outstanding at December 31, 2017 compared to $702.5 million at December 31, 2016. 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 income (loss), 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 losses of $(5.5) million, $(0.4) million, and $(2.6) million in 2017, 2016, and 2015, respectively. The Company enters into foreign currency forward exchange contracts to mitigate the effects of adverse fluctuations in foreign currency exchange rates on these transactions. These contracts generally have a short duration and are recorded at fair value with both realized and unrealized gains and losses recorded in Other income, net. The net gain (loss) from these contracts was $0.8 million, $(0.3) million, and $(0.1) million in 2017, 2016, and 2015, 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, 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 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, 2017 and 2016.

Stock repurchase programs. The Company records the cost to repurchase its own common shares to treasury stock. During 2017, 2016 and 2015, the Company used $41.3 million, $59.0 million, and $509.0 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 did not adopt any significant new accounting standards during 2017.

Accounting standards issued but not yet adopted. The FASB has issued accounting standards that have not yet become effective and that may impact the Company’s consolidated financial statements or related disclosures in future periods. These standards and their potential impact are discussed below:

Accounting standards effective in 2018

Stock Compensation Award Modifications — In May 2017, the FASB issued 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. ASU No. 2017-09 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-09 will not have a material impact on the Company's consolidated financial statements.

Retirement Benefits Cost Presentation — In March 2017, the FASB issued 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, and provides additional guidance on the presentation of net benefit cost in the income statement and clarifies the components eligible for capitalization. ASU No. 2017-07 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-07 will not have a material impact on the Company's consolidated financial statements.

Partial Sales of Non-financial Assets — In February 2017, the FASB issued 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 recently established guidance on non-financial asset de-recognition as well as the accounting for partial sales of non-financial assets. It conforms the de-recognition guidance on non-financial assets with the model for revenue transactions. ASU No. 2017-05 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-05 will not have a material impact on the Company's consolidated financial statements.

Definition of a Business — In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU No. 2017-01"), which was effective for Gartner on January 1, 2018. ASU No. 2017-01 changes the U.S. GAAP definition of a business which can impact the accounting for asset purchases, acquisitions, goodwill impairment, and other assessments. We have concluded that the adoption of ASU No. 2017-01 will not have a material impact on the Company's consolidated financial statements.

Presentation of Restricted Cash — In November 2016, the FASB issued 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 shown on the statement of cash flows. If different, a reconciliation of the cash balances reported in the cash flow statement and the balance sheet would need to be provided along with explanatory information. ASU No. 2016-18 was effective for Gartner on January 1, 2018. The adoption of ASU No. 2016-18 will require the Company to disclose restricted cash and, as a result, will change the presentation of its consolidated statements of cash flows.

Income Taxes — In October 2016, the FASB issued 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 and was effective for Gartner on January 1, 2018. Current U.S. GAAP requires deferral of the income tax implications of an intercompany sale of assets until the assets are sold to a third party or recovered through use. Under the new rule, the seller’s tax effects and the buyer’s deferred taxes on post-adoption asset transfers will be immediately recognized upon the sale. On the date of adoption of ASU No. 2016-16 any taxes attributable to pre-2018 intra-entity transfers that were previously deferred will be accelerated and recorded to accumulated earnings as permitted by the transition rules. ASU 2016-16 could have a material impact on our consolidated financial statements in the future depending on the nature, size, and tax consequences of future intra-entity transfers, if any.

Statement of Cash Flows — In August 2016, the FASB issued 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. ASU No. 2016-15 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2016-15 will not have a material impact on the Company's consolidated financial statements.

Financial Instruments Recognition and Measurement — In January 2016, the FASB issued 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 will be measured at fair value with changes in fair value recognized in net income. ASU No. 2016-01 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2016-01 will not have a material impact on the Company's consolidated financial statements.

Revenue Recognition — In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments require changes in revenue recognition policies as well as enhanced disclosures. ASU No. 2014-09 is intended to clarify the principles for recognizing revenue by removing inconsistencies and weaknesses in 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. ASU No. 2014-09 also requires significantly expanded disclosures around the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. An entity may adopt ASU No. 2014-09 using either a full retrospective approach for each prior reporting period presented or a modified retrospective approach (the cumulative effect method). The Company adopted ASU No. 2014-09 on January 1, 2018 using the cumulative effect method of adoption. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. The adoption of the standard does require the Company to reclassify certain immaterial amounts in the Company’s consolidated balance sheet as well as provide the enhanced disclosures required by the standard, both of which will be provided in the Company's Form 10-Q filing for the quarterly period ending March 31, 2018.

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 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 the hedge accounting guidance in current U.S. GAAP. ASU No. 2017-12 is effective for Gartner on January 1, 2019. We are currently evaluating the impact of ASU No. 2017-12 on the Company's consolidated financial statements.

Distinguishing Liabilities from Equity — In July 2017, the FASB issued ASU No. 2017-11, "Earnings Per Share, Distinguishing Liabilities from Equity, and Derivatives and Hedging" ("ASU No. 2017-11"). ASU No. 2017-11 is intended to simplify the accounting for financial instruments with characteristics of liabilities and equity. Among the issues addressed are: (i) determining whether an instrument (or embedded feature) is indexed to an entity’s own stock; (ii) distinguishing liabilities from equity for mandatorily redeemable financial instruments of certain nonpublic entities; and (iii) identifying mandatorily redeemable non-controlling interests. ASU No. 2017-11 is effective for Gartner on January 1, 2019. We are currently evaluating the potential impact of ASU No. 2017-11 on the Company's consolidated financial statements.

Leases — In February 2016, the FASB issued ASU No. 2016-02, "Leases" ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure for lease arrangements. Currently under U.S. GAAP, lease arrangements that meet certain criteria are considered operating leases and are not recorded on the balance sheet. All of the Company's existing lease arrangements are accounted for as operating leases and are thus not recorded on the Company's balance sheet. ASU No. 2016-02 will significantly change the accounting for leases since a right-of-use ("ROU") model must be used in which the lessee must record a ROU asset and a lease liability on the balance sheet for leases with terms longer than 12 months. Leases will be classified as either finance or operating arrangements, with classification affecting the pattern of expense recognition in the income statement. ASU No. 2016-02 also requires expanded disclosures about leasing arrangements. ASU No. 2016-02 will be effective for Gartner on January 1, 2019. We are currently evaluating the potential impact of ASU No. 2016-02 on our consolidated financial statements.

Accounting standards effective in 2020

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 current goodwill impairment test. ASU No. 2017-04 is effective for Gartner on January 1, 2020. We have concluded that the adoption of ASU No. 2017-04 will not 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 also 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. However, since these standards have not yet been issued, the effective dates and potential impact are unknown.

Acquisitions and Divestiture

12 Months Ended

Dec. 31, 2017

Mergers, Acquisitions And Dispositions Disclosures [Abstract]

ACQUISITIONS AND DIVESTITURE

Acquisitions

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 completed the following business acquisitions:

For the year ended December 31, 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 (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 (5)	$	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 from these businesses and for cash flow reporting purposes, the Company paid a total of $2.63 billion in cash.


(3)	The Company borrowed a total of approximately $2.8 billion in conjunction with the CEB acquisition (see Note 7 — 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.


(5)	The Company may also be required to pay up to an additional $20.8 million in cash for L2 which is contingent on the achievement of certain employment conditions by several key employees. This amount is being recognized as compensation expense over approximately three years.

Preliminary Allocation of Purchase Price

The following table summarizes the preliminary 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. The Company recorded certain measurement period adjustments to the CEB preliminary purchase price allocation during 2017, primarily related to tenant improvement incentives and tax liabilities. These adjustments resulted in a net increase to recorded goodwill of approximately $32.0 million. As of December 31, 2017, the allocation of the purchase price for the L2 and CEB acquisitions are preliminary with respect to certain tax matters and contingencies. The Company will resolve these remaining matters and complete the allocation of the purchase price by the end of the accounting measurement period for the respective acquisition.

(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, Events, and Talent Assessment & 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; and

(c) An adjustment for additional depreciation and amortization expense as a result of the preliminary 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.

The Company recognized $158.5 million of acquisition and integration charges in 2017 compared to $42.6 million in 2016. The additional charges during 2017 primarily consisted of higher professional fees, severance, stock-based compensation charges, and accruals for exit costs for certain office space that the Company does not intend to occupy in Arlington, Virginia that was related to the CEB acquisition. The following table presents a summary of the activity related to this space for the year ended December 31, 2017 (in thousands):



Liability balance at December 31, 2016	$	—
Charges and adjustments	13,087
Payments	(126		)
Liability balance at December 31, 2017	$	12,961

For the year ended December 31, 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 Events segments. The Company also recorded an additional $1.9 million of additional goodwill in 2016 related to a prior year acquisition.

For the year ended December 31, 2015:

The Company acquired 100% of the outstanding shares of Nubera eBusiness S.L., and Capterra, Inc., during 2015. Each of these businesses assist clients with selecting business software. The aggregate purchase price was $206.9 in cash. Net of cash acquired with the businesses and for cash flow reporting purposes the Company paid $196.2 million in cash. The Company recorded $79.6 million and $138.1 million of amortizable intangible assets and goodwill, respectively, and $10.8 million in liabilities on a net basis for these acquisitions. The operating results and the related goodwill are reported as part of the Company's Research segment.

Planned divestiture of the CEB Talent Assessment business

On February 6, 2018, the Company announced that it had reached a definitive agreement to sell its CEB Talent Assessment business for approximately $400.0 million. The agreement was the result of a previously announced process to evaluate strategic alternatives for the business. The purchase price is subject to typical adjustments for, among other things, the working capital of the business. The transaction is expected to close in the first half of 2018 and is subject to customary closing conditions and certain approvals.

The CEB Talent Assessment business was acquired by Gartner as part of the CEB acquisition in 2017 and is a significant portion of the Talent Assessment & Other segment. During the period from the CEB acquisition date to December 31, 2017, the CEB Talent Assessment business contributed approximately $126.1 million of revenue and incurred a pre-tax loss of approximately $19.3 million. Effective with its designation as held-for-sale on October 4, 2017, we discontinued recording depreciation and amortization on the property, equipment and leasehold improvements and finite-lived intangible assets of this business as required under the accounting rules. The Company also separately classified the related assets and liabilities of this business as held-for-sale in its December 31, 2017 Consolidated Balance Sheet.

The principal components of the held-for-sale assets and liabilities at December 31, 2017 for this business are summarized in the table below (in thousands):



Cash and cash equivalents	$	10,000
Fees receivable, net	50,928
Goodwill	212,994
Intangible assets, net	250,472
Other assets, including property, equipment and leasehold improvements, net	18,571
Total assets held-for-sale	$	542,965

Accounts payable and accrued liabilities	$	32,388
Deferred revenues	61,450
Deferred tax liabilities	47,404
Other liabilities	4,603
Total liabilities held-for-sale	$	145,845

The sale of the business has been structured as a sale of the shares of the affected subsidiaries with the corresponding deferred taxes being transferred to the buyer upon consummation of the sale. As such, the Company made an accounting policy election to classify the deferred taxes associated with the individual assets and liabilities that are part of the transaction as held-for-sale.

Other Assets

12 Months Ended

Dec. 31, 2017

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

OTHER ASSETS

Other assets consist of the following (in thousands):



	December 31,
	2017		2016
Benefit plan-related assets	$	97,525	$	45,958
Non-current deferred tax assets	31,067		27,275
Other	65,150		14,046
Total other assets	$	193,742	$	87,279

Accounts Payable, Accrued, and Other Liabilities

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

ACCOUNTS PAYABLE, ACCRUED, AND OTHER LIABILITIES

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



	December 31,
	2017		2016
Accounts payable	$	49,000	$	41,009
Payroll and employee benefits payable	120,278		87,821
Severance and retention bonus payable	44,685		22,425
Bonus payable	162,710		105,549
Commissions payable	108,969		68,273
Taxes payable	46,758		20,378
Other accrued liabilities	134,421		95,316
Total accounts payable and accrued liabilities	$	666,821	$	440,771

Other liabilities consist of the following (in thousands):



	December 31,
	2017		2016
Non-current deferred revenue	$	16,205	$	11,289
Long-term taxes payable	66,386		19,737
Benefit plan-related liabilities	118,868		67,747
Lease-related matters	115,840		38,042
Non-current deferred tax liabilities	206,338		22,520
Other	54,362		22,482
Total other liabilities	$	577,999	$	181,817

Debt

12 Months Ended

Dec. 31, 2017

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. As of December 31, 2017, the 2016 Credit Agreement provides 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, 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 its 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 $300.0 million 364-day Bridge Credit Facility discussed below, were used to fund the CEB acquisition and related costs. As discussed below, the funds borrowed under the 364-day Bridge Credit Facility were completely repaid during 2017.

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 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 with its lenders 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 will be 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 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 Incremental 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 average rate on Federal Reserve Board of New York rate 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.

The Term loan B facility contains representations and warranties, affirmative and negative covenants and events of default that are the same as the Term loan A facility and revolving credit facility, except that a breach of financial maintenance covenants will not result in an event of default under the Term loan B facility unless the lenders under the revolving credit facility and Term loan A facility have accelerated the revolving loans and Term loan A loans and terminated their commitments thereunder. Additionally, the Term loan B facility includes mandatory prepayment requirements related to asset sales (subject to reinvestment), debt incurrence (other than permitted debt) and excess cash flow, subject to certain limitations described therein. The Term loan B facility will mature on April 5, 2024 and amounts outstanding thereunder will bear 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, in conjunction with the acquisition of CEB, 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, in conjunction with the acquisition of CEB, 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 also used to fund a portion of the purchase price associated with the CEB acquisition.

The Senior Notes were issued at an issue price of 100.00% 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 will 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 40.0% 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 specific kinds of change 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 - December 31, 2017

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



	Balance December 31,			Balance December 31,
Description:	2017			2016
2016 Credit Agreement - Term loan A facility (1)	$	1,429,312		$	585,000
2016 Credit Agreement - Term loan B facility (1)	496,250			—
2016 Credit Agreement - Revolving credit facility (1), (2)	595,000			115,000
Senior notes (3)	800,000			—
Other (4)	2,500			2,500
Principal amount outstanding (5), (6)	3,323,062			$	702,500
Less: deferred financing fees (7)	(44,217		)	(8,109		)
Net balance sheet carrying amount	$	3,278,845		$	694,391

(1)

The contractual annualized interest rate as of December 31, 2017 on the Term loan A and B facilities was 3.57%, which consisted of a floating Eurodollar base rate of 1.57% plus a margin of 2.00%. The contractual annualized interest rate on the revolving credit facility was 4.07%, which consisted of a floating eurodollar base rate of 1.57% plus a margin of 2.50%. However, the Company has interest rate swap contracts which effectively convert the floating eurodollar base rates on a portion of the amounts outstanding to a fixed base rate.


(2)	The Company had $558.0 million of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2017.


(3)	Consists of an $800.0 million principal amount of Senior Notes outstanding. The Senior Notes pay a fixed rate of 5.125% and have an eight year maturity.


(4)	Consists of a $2.5 million State of Connecticut economic development loan with a 3.0% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. Principal payments are deferred for the first five years and the loan may be repaid at any point by the Company without penalty.


(5)	The average annual interest rate on the Company's outstanding debt as of December 31, 2017 was 3.91%, including the effect of its interest rate swaps discussed below.


(6)	The contractual due dates by year on the debt outstanding as of December 31, 2017 are as follows: $80.0 million in 2018; $107.6 million in 2019; $144.7 million in 2020; $42.6 million in 2021; $1.68 billion in 2022; and approximately $1.27 billion thereafter. In January 2018 the Company repaid $255.0 million of outstandings on the revolver which were not contractually due until 2022.


(7)	The deferred financing fees are being amortized to Interest expense, net over the term of the respective debt obligation. 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

As of December 31, 2017, the Company had fixed-for-floating interest rate swap contracts. The swaps have a total notional value of $1.4 billion and mature in 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 1.54% to 2.13% and in return receives a floating eurodollar base rate on $1.4 billion of 30-day notional borrowings.

The Company accounts for the interest rate swaps 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 change in the fair value of the hedges is recorded in earnings. All of the swaps were highly effective hedges of the forecasted interest payments as of December 31, 2017. The interest rate swaps had a positive fair value of $3.4 million at December 31, 2017 and a negative fair value of $2.3 million as of December 31, 2016. These amounts were deferred and classified in accumulated other comprehensive income (loss), net of tax effect.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

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 2018 and 2032. The future minimum annual cash payments under these operating lease agreements as of December 31, 2017 was as follows (in thousands):



Year ended December 31,
2018	$	129,570
2019	121,543
2020	113,612
2021	106,371
2022	97,225
Thereafter	727,405
Total minimum lease payments (1)	$	1,295,726

(1) Excludes approximately $284.0 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, 2017, the Company did not have any material payment obligations under any such indemnification agreements.

Stockholders' Equity

12 Months Ended

Dec. 31, 2017

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 which may limit our ability to pay dividends. The following table summarizes transactions relating to our Common Stock for the three years ended December 31, 2017:



	Issued Shares	Treasury Stock Shares
Balance at December 31, 2014	156,234,415	68,713,890
Issuances under stock plans	—	(1,003,746	)
Purchases for treasury (1)	—	6,186,101
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


(1)	The Company used a total of $41.3 million, $59.0 million, and $509.0 million in cash for share repurchases in 2017, 2016, and 2015, respectively.

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 Divestiture 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 approved authorization to repurchase the Company's common stock, of which $1.1 billion remained available as of December 31, 2017. The Company may repurchase its common stock from time to time in amounts and at prices 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, private transactions or other transactions and will be funded from cash on hand and borrowings under the Company’s credit arrangement.

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

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	)
Changes during the period:
Change in AOCL/I before reclassifications to income	(1,492		)	—			47,363			45,871
Reclassifications from AOCL/I to income during the period (2), (3)	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

2016



	Interest Rate Swaps			Defined Benefit Pension Plans			Foreign Currency Translation Adjustments			Total
Balance - December 31, 2015	$	(3,079	)	$	(4,832	)	$	(36,491	)	$	(44,402	)
Changes during the period:
Change in AOCL/I before reclassifications to income	(2,902		)	(1,113		)	(5,986		)	(10,001		)
Reclassifications from AOCL/I to income during the period (2), (3)	4,572			148			—			4,720
Other comprehensive income (loss) for the period	1,670			(965		)	(5,986		)	(5,281		)
Balance - December 31, 2016	$	(1,409	)	$	(5,797	)	$	(42,477	)	$	(49,683	)

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

(2) 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.

(3) The reclassifications related to defined benefit pension plans were 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.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

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. At December 31, 2017, the Company had 5.7 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 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 complex and 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	2017		2016		2015
Stock appreciation rights	$	5.6	$	5.6	$	5.7
Restricted stock units	72.6		40.4		39.8
Common stock equivalents	0.7		0.7		0.6
Total (1)	$	78.9	$	46.7	$	46.1



Expense category line item	2017		2016		2015
Cost of services and product development	$	25.8	$	21.9	$	20.6
Selling, general and administrative	35.5		24.8		25.5
Acquisition and integration charges (2)	17.6		—		—
Total (1)	$	78.9	$	46.7	$	46.1


(1)	Includes charges of $22.9 million, $19.4 million and $20.1 million during 2017, 2016 and 2015, respectively, for awards to retirement-eligible employees. Those awards vest on an accelerated basis.


(2)	These charges are primarily the result of the acceleration of the vesting of certain restricted stock units related to the CEB acquisition.

As of December 31, 2017, the Company had $79.9 million of total unrecognized stock-based compensation cost, which is expected to be expensed over the remaining weighted average service period of approximately 2.4 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, 2017:



	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, 2016	1.3		$	66.22	$	15.77	4.40 years
Granted	0.3		99.07		22.02		6.10 years
Forfeited	(0.1	)	85.28		10.49		n/a
Exercised	(0.3	)	52.72		14.85		n/a
Outstanding at December 31, 2017 (1) (2)	1.2		$	76.73	$	17.35	4.28 years
Vested and exercisable at December 31, 2017 (2)	0.5		$	65.67	$	15.69	3.22 years

n/a = not applicable


(1)	As of December 31, 2017, 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, 2017, the total SARs outstanding had an intrinsic value of $55.0 million. On such date, SARs vested and exercisable had an intrinsic value of $30.2 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:



	2017		2016		2015
Expected dividend yield (1)	—	%	—	%	—	%
Expected stock price volatility (2)	22	%	22	%	24	%
Risk-free interest rate (3)	1.8	%	1.1	%	1.5	%
Expected life in years (4)	4.53		4.39		4.41


(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 an 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, 2017:



	Restricted Stock Units ("RSUs") (in millions)		Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016	1.3		$	73.19
Granted (1) (2)	1.1		105.55
Vested and released	(0.8	)	79.60
Forfeited	(0.1	)	91.03
Outstanding at December 31, 2017 (3) (4)	1.5		$	91.47


(1)	The 1.1 million of RSUs granted during 2017 consisted of 0.2 million of performance-based RSUs awarded to executives and 0.9 million of service-based RSUs awarded to executives, non-executive employees and non-management board members. The 0.2 million of performance-based RSUs represents the target amount of the grant for the year, which is tied to the increase

in heritage Gartner’s total contract value for 2017. Total contract value for this determination represents the value attributable to all of heritage Gartner’s subscription-related revenue contracts. The final number of performance-based RSUs awarded could range from 0% to 200% of the target amount. The actual increase in heritage Gartner’s contract value for 2017 as measured on December 31, 2017 yielded approximately 186% of the target amount. The incremental awards based on the actual achievement under the 2017 grant will be issued in 2018.


(2)	Includes 0.6 million of RSUs awarded to employees that joined Gartner as a result of the CEB acquisition.


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


(4)	As of December 31, 2017, the weighted average remaining contractual term of the RSUs outstanding was approximately 1.2 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, 2017:



	Common Stock Equivalents ("CSEs")		Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016	107,338		$	20.74
Granted	5,852		120.28
Converted to shares of Common Stock upon grant	(3,177	)	119.10
Outstanding at December 31, 2017	110,013		$	23.19

Employee Stock Purchase Plan

The Company has an employee stock purchase plan (the “ESP Plan”) under which 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, 2017, the Company had 0.8 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 $11.7 million, $9.3 million and $7.5 million in cash from employee share purchases under the ESP Plan during 2017, 2016 and 2015, respectively.

Computation of Earnings Per Share

12 Months Ended

Dec. 31, 2017

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 reconciliation of the basic and diluted earnings per share computations for the years ended December 31 (in thousands, except per share amounts):



	2017		2016		2015
Numerator:
Net income used for calculating basic and diluted earnings per common share	$	3,279	$	193,582	$	175,635
Denominator: (1)
Weighted average number of common shares used in the calculation of basic earnings per share	88,466		82,571		83,852
Common share equivalents associated with stock-based compensation plans	1,324		1,249		1,204
Shares used in the calculation of diluted earnings per share	89,790		83,820		85,056
Earnings per share: (2)
Basic	$	0.04	$	2.34	$	2.09
Diluted	$	0.04	$	2.31	$	2.06


(1)	The Company repurchased 0.4 million, 0.6 million and 6.2 million shares of its Common Stock in 2017, 2016 and 2015, respectively.


(2)	Both basic and diluted earnings per share for 2017 include a one-time benefit of approximately $0.66 per share related to the Tax Cuts and Jobs Act of 2017. Note 10 — Income Taxes provides information related to the Tax Cuts and Jobs Act of 2017.

The following table presents the number of common share equivalents that were not included in the computation of diluted EPS in the table above 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.



	2017		2016		2015
Anti-dilutive common share equivalents as of December 31 (in millions):	0.3		0.2		0.3
Average market price per share of Common Stock during the year	$	116.09	$	92.58	$	86.02

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

INCOME TAXES

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



	2017			2016		2015
U.S.	$	(135,757	)	$	182,178	$	165,848
Non-U.S.	7,940			106,253		106,363
(Loss) income before income taxes	$	(127,817	)	$	288,431	$	272,211

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



	2017			2016			2015
Current tax expense:
U.S. federal	$	48,339		$	58,616		$	48,801
State and local	434			11,292			10,300
Foreign	38,602			27,536			23,225
Total current	87,375			97,444			82,326
Deferred tax (benefit) expense:
U.S. federal	(176,046		)	(61		)	(884		)
State and local	(14,363		)	(349		)	(702		)
Foreign	(25,898		)	(1,626		)	1,550
Total deferred	(216,307		)	(2,036		)	(36		)
Total current and deferred	(128,932		)	95,408			82,290
Benefit (expense) relating to interest rate swaps used to increase (decrease) equity	(2,477		)	(1,113		)	893
Benefit from stock transactions with employees used to increase equity	46			52			13,960
Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity	267			502			(567		)
Total tax (benefit) expense	$	(131,096	)	$	94,849		$	96,576

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



	December 31,
	2017			2016
Accrued liabilities	$	80,557		$	62,439
Loss and credit carryforwards	59,502			7,766
Assets relating to equity compensation	24,874			25,569
Other assets	30,236			6,652
Gross deferred tax assets	195,169			102,426
Property, equipment, and leasehold improvements	(962		)	(11,796		)
Intangible assets	(372,542		)	(43,548		)
Prepaid expenses	(35,126		)	(32,971		)
Other liabilities	(6,584		)	(7,925		)
Gross deferred tax liabilities	(415,214		)	(96,240		)
Valuation allowance	(3,192		)	(1,431		)
Net deferred tax (liabilities) assets	$	(223,237	)	$	4,755

Net deferred tax assets and net deferred tax liabilities were $30.5 million and $253.7 million as of December 31, 2017, respectively, and $27.3 million and $22.5 million as of December 31, 2016, respectively. These amounts are primarily 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, 2017.

The valuation allowances of $3.2 million as of December 31, 2017 and $1.4 million as of 2016, primarily relate to net operating losses which are not likely to be realized.

As of December 31, 2017, the Company had state and local tax net operating loss carryforwards of $91.5 million, of which $0.9 million expire within one to five years and $19.9 million expire within six to fifteen years and $70.7 million expire within sixteen to twenty years. The Company also had state tax credits of $2.0 million, a majority of which will expire in five to six years. As of December 31, 2017, the Company had non-U.S. net operating loss carryforwards of $16.0 million, of which $0.5 million expire over the next 20 years and $15.5 million can be carried forward indefinitely. In addition, the Company also had foreign tax credit carryforwards of $59.0 million, all of which will expire at the end of 2027. These amounts have been reduced for associated unrecognized tax benefits, consistent with FASB ASU No. 2013-11.

As of December 31, 2017, the Company recorded deferred tax assets for federal and state unrealized capital losses of $62.9 million resulting from held-for-sale accounting for the CEB Talent Assessment business.

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:



	2017		2016		2015
Statutory tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	3.6		2.4		3.5
Effect of non-U.S. operations	5.9		(6.1	)	(6.9	)
Record (release) reserve for tax contingencies	(2.8	)	3.2		1.7
Law changes	41.8		—		(0.2	)
Excess tax benefits from stock based compensation	11.0		(3.8	)	—
Nondeductible acquisition costs	(7.9	)	2.6		0.8
Nondeductible meals and entertainment costs	(3.5	)	1.1		1.1
Capital loss	13.1		—		—
Record (release) valuation allowance	3.0		(0.2	)	0.5
Other items, net	3.4		(1.3	)	—
Effective tax rate	102.6	%	32.9	%	35.5	%

The 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, 2017, we have not completed our accounting for the tax effects of enactment of the Act because all of the necessary information is not currently available, prepared or analyzed. As such, the amount we have recorded are provisional estimates and as permitted by SEC per Staff Accounting Bulletin No. 118, we will continue to assess the enactment of the Act and may record additional provisional amount or adjustments to provisional amounts during fiscal year 2018. We expect to complete the accounting for these impacts of tax reform by the fourth quarter of 2018 as we complete our analysis and receive additional guidance from the Internal Revenue Service pertaining to 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% and recorded a provisional amount which reduced our income tax expense by $123.2 million. However, we are still finalizing purchase accounting for the acquisition of CEB, analyzing certain aspects of the Act and refining our deferred tax calculations, which could affect the measurement of these balances or give rise to new deferred tax amounts.

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 US income taxes. We recorded a $63.6 million provisional amount for this one-time transition tax liability, resulting in an increase in income tax expense of $63.6 million. We have not yet completed our calculation of the tax on ADFI given pending regulatory guidance and the need to obtain, prepare and analyze various information relevant to calculation including, but not limited to, our post-1986 E&P, foreign taxes and amounts held in cash or other specified assets on various measurement dates.

As disclosed in Note 1 - Business and Significant Accounting Policies, the Company adopted FASB ASU No. 2016-09 in 2016. The effect of the adoption reduced the provision for income taxes by $12.9 million and $10.0 million for the years ended December 31, 2017 and 2016, respectively.

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 associated with this decision. 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, 2017 and December 31, 2016, the Company had unrecognized tax benefits of $60.3 million and $37.1 million, respectively. The increase is primarily attributable to pre-acquisition unrecognized tax benefits of CEB for positions taken with respect to intercompany transactions and state income tax positions. The unrecognized tax benefits as of December 31, 2017 related primarily to the exclusion of stock-based compensation expense from the Company’s cost sharing agreement, utilization of certain tax attributes, state income tax positions, the ability to realize certain refund claims, and intercompany transactions. It is reasonably possible that unrecognized tax benefits will be decreased by $6.3 million within the next 12 months due to anticipated closure of audits and the expiration of certain statutes of limitation.

Included in the balance of unrecognized tax benefits at December 31, 2017 are potential benefits of $57.1 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, 2017 are potential benefits of $3.2 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):



	2017			2016
Beginning balance	$	37,099		$	25,911
Additions based on tax positions related to the current year	10,883			7,086
Additions for tax positions of prior years	24,299			6,443
Reductions for tax positions of prior years	(10,613		)	(496		)
Reductions for expiration of statutes	(1,368		)	(1,006		)
Settlements	(1,769		)	(544		)
Change in foreign currency exchange rates	1,738			(295		)
Ending balance	$	60,269		$	37,099

The Company accrues interest and penalties related to unrecognized tax benefits in its income tax provision. As of December 31, 2017 and 2016, the Company had $6.4 million and $4.3 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 both the years ended December 31, 2017 and December 31, 2016 was $0.9 million.

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 the U.S. states, the United Kingdom, Canada, Japan, France, and Ireland, the Company's statutes vary and are open as far back as 2012.

Under U.S. GAAP rules, 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. While our current plans do not demonstrate a need to repatriate accumulated undistributed foreign earnings to fund our U.S. operations or otherwise satisfy the liquidity needs of our U.S. operations, the Company has not asserted its intention to indefinitely reinvest certain accumulated undistributed foreign earnings of CEB. As a result of tax planning, approximately $12.0 million of deferred tax liability previously recorded in purchase accounting for the estimated tax that could result from the remittance of these earnings was reversed in the current quarter and related goodwill reduced. The Company continues to assert its intention to reinvest all other 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 $194.0 million as of December 31, 2017. 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, 2017

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 No. 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 outstanding contracts):

December 31, 2017



Derivative Contract Type	Number of Outstanding Contracts	Notional Amounts		Fair Value Asset (Liability) (3)		Balance Sheet Line Item	Unrealized Gain Recorded in OCI
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

December 31, 2016



Derivative Contract Type	Number of Outstanding Contracts	Notional Amounts		Fair Value Asset (Liability) (3)			Balance Sheet Line Item	Unrealized Loss Recored in OCI
Interest rate swaps (1)	3	$	700,000	$	(2,349	)	Other liabilities	$	(1,409	)
Foreign currency forwards (2)	84	86,946		(320		)	Accrued liabilities	—
Total	87	$	786,946	$	(2,669	)		$	(1,409	)


(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 AOCL/I, net of tax effect (see Note 5 — Debt for additional information).

(2)

The Company has foreign exchange transaction risk since 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 since the Company does not designate these contracts as hedges for accounting purposes. All of the outstanding contracts at December 31, 2017 matured by the end of January 2018.


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

At December 31, 2017, 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:	2017			2016		2015
Interest expense (1)	$	7.9		$	7.6	$	8.5
Other (gain) loss, net (2)	(0.8		)	0.3		0.1
Total expense	$	7.1		$	7.9	$	8.6


(1)	Consists of interest 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, 2017

Fair Value Disclosures [Abstract]

FAIR VALUE DISCLOSURES

The Company’s financial instruments include cash equivalents, fees receivable from customers, accounts payable, and accruals which are normally short-term in nature. The Company believes the carrying amounts of these financial instruments reasonably approximate their fair value 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 the carrying amount of its variable-rate borrowings reasonably approximates their fair value because the rate of interest on those borrowings reflects 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 upon the transparency of inputs used in the valuation of assets and liabilities. Classification within the hierarchy is based upon 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 fair value hierarchy.

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



	Fair Value		Fair Value
Description:	December 31, 2017		December 31, 2016
Assets:
Values based on Level 1 inputs:
Deferred compensation plan assets (1)	$	29,108	$	10,252
Total Level 1 inputs	29,108		10,252
Values based on Level 2 inputs:
Deferred compensation plan assets (1)	59,017		27,847
Foreign currency forward contracts (2)	2,053		165
Interest rate swap contracts (3)	3,412		—
Total Level 2 inputs	64,482		28,012
Total Assets	$	93,590	$	38,264
Liabilities:
Values based on Level 2 inputs:
Deferred compensation plan liabilities (1)	$	89,900	$	43,075
Foreign currency forward contracts (2)	1,605		485
Interest rate swap contracts (3)	—		2,349
Senior Notes due 2025 (4)	837,560		—
Total Level 2 inputs	$	929,065	$	45,909
Total Liabilities	$	929,065	$	45,909

(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 and 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 these assets had a fair value of $29.1 million and $10.3 million as of December 31, 2017 and 2016, respectively. The carrying amount of the life insurance contracts equals their cash surrender value. Cash surrender value represents the estimated amount that the Company would receive upon termination of the contract, which approximates fair value. The Company considers the life insurance contracts to be valued based on a Level 2 input, and these assets had a fair value of $59.0 million and $27.8 million at December 31, 2017 and 2016, 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 the foreign currency forward 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 which hedge the risk of variability from interest payments on its borrowings (see Note 5 — Debt). The fair value of the swaps is based on mark-to-market valuations prepared by a third-party broker. The 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 issued $800.0 million of principal amount fixed-rate Senior Notes due 2025 on March 30, 2017. 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, 2017

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 upon the level of employee contributions, up to a maximum of 4% of an employee’s eligible salary, subject to an annual maximum. For 2017, the maximum match was $7,200. Amounts expensed in connection with the 401k Plans totaled $29.8 million, $22.9 million and $20.0 million in 2017, 2016 and 2015, 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 $88.1 million and $38.1 million at December 31, 2017 and 2016, respectively (see Note 12 — Fair Value Disclosures for fair value information). The corresponding deferred compensation liability, which was $89.9 million and $43.1 million at December 31, 2017 and 2016, 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 the plans was $0.4 million, $0.1 million and $0.5 million in 2017, 2016 and 2015, 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 No. 715 and 960. The following are the components of defined benefit pension expense for the years ended December 31 (in thousands):



	2017			2016			2015
Service cost	$	2,820		$	2,780		$	2,620
Interest cost	765			850			790
Expected return on plan assets	(360		)	(375		)	(345		)
Recognition of actuarial loss	350			200			300
Recognition of termination benefits	—			—			85
Total defined benefit pension plan expense (1)	$	3,575		$	3,455		$	3,450


(1)	Pension expense is classified in SG&A in the Consolidated Statements of Operations.

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



	2017		2016		2015
Weighted average discount rate (1)	1.78	%	1.78	%	2.19	%
Average compensation increase	2.66	%	2.67	%	2.66	%


(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):



	2017			2016			2015
Projected benefit obligation at beginning of year	$	38,400		$	35,870		$	38,115
Service cost	2,820			2,780			2,620
Interest cost	765			850			790
Actuarial loss (gain) due to assumption changes and plan experience	690			1,480			(1,190		)
Additions and contractual termination benefits	(860		)	—			85
Benefits paid (1)	(920		)	(1,640		)	(775		)
Foreign currency impact	4,555			(940		)	(3,775		)
Projected benefit obligation at end of year (2)	$	45,450		$	38,400		$	35,870


(1)	The Company projects the following benefit payments will be made in future years to plan participants: $1.3 million in 2018; $2.2 million in 2019; $1.5 million in 2020, $1.5 million in 2021, $1.6 million in 2022; and $10.5 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:	2017			2016			2015
Projected benefit obligation	$	45,450		$	38,400		$	35,870
Pension plan assets at fair value (1)	(18,475		)	(14,465		)	(13,190		)
Funded status – shortfall (2)	$	26,975		$	23,935		$	22,680



Amounts recorded in the Consolidated Balance Sheets for the plans:
Other liabilities — accrued pension obligation (2)	$	26,975		$	23,935		$	22,680
Stockholders’ equity — deferred actuarial loss (3)	$	(5,861	)	$	(5,797	)	$	(4,832	)

(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 No. 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 2.22%, 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, 2017, the Company contributed $2.4 million to these plans, and benefits paid to participants were $1.8 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, 2017 is recorded in AOCL/I and will be reclassified out of AOCL/I and recognized as pension expense over approximately 13 years, subject to certain limitations set forth in FASB ASC Topic No. 715. The impact of this amortization on pension expense in 2018 is projected to result in approximately $0.3 million of additional expense. The amortization of deferred actuarial losses from AOCL/I to pension expense in each of the three years ended December 31, 2017 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 the plans. The reinsurance asset is not a pension plan asset but is an asset of the Company. At December 31, 2017 and 2016, the reinsurance asset was recorded at its cash surrender value of $9.1 million and $7.8 million, respectively, and is classified in Other assets on the Company's Consolidated Balance Sheets. The Company believes the cash surrender value approximates fair value and is equivalent to a Level 2 input under the FASB’s fair value framework in ASC Topic No. 820.

Segment Information

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

SEGMENT INFORMATION

As a result of the CEB acquisition on April 5, 2017, the Company began reporting its results across four business segments reflecting its enlarged scale and breadth of advisory services aligned to the mission-critical priorities of virtually all functional business leaders across every industry and size of enterprise worldwide.

Our products and services are delivered through four segments – Research, Consulting, Events and Talent Assessment & Other, 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, 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.


•	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.


•	Events provides business professionals across the organization the opportunity to learn, share and network. From our flagship CIO event Gartner Symposium/ITxpo, to industry-leading conferences focused on specific business roles and topics, to member-driven sessions, our events enable attendees to experience the best of Gartner insight and advice live.


•	Talent Assessment & Other helps organizations assess, engage, manage and improve talent. This is accomplished through knowledge and skills assessments, training programs, workshops, and survey and questionnaire services.

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 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 operating information about the Company’s reportable segments for the periods indicated (in thousands):



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

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

	Research		Consulting		Events		Talent Assessment & Other	Consolidated
2015 (1)
Revenues	$	1,614,904	$	296,317	$	251,835	—	$	2,163,056
Gross contribution	1,117,534		86,486		130,527		—	1,334,547
Corporate and other expenses								(1,046,550		)
Operating income								$	287,997

(1) In 2017 the Company began reporting the results of its Strategic Advisory Services ("SAS") business in Research whereas previously the SAS business was reported with Consulting. Although the impact of the reclassification was not significant, the operating results of the SAS business for 2016 and 2015 were reclassified from Consulting to Research to be comparable with the current year presentation.

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



	2017			2016		2015
Total segment gross contribution	$	2,000,386		$	1,512,000	$	1,334,547
Costs and expenses:
Cost of services and product development - unallocated (1)	9,090			13,108		10,567
Selling, general and administrative	1,599,004			1,089,184		962,677
Depreciation and amortization	240,171			61,969		47,131
Acquisition and integration charges	158,450			42,598		26,175
Operating (loss) income	(6,329		)	305,141		287,997
Interest expense and other, net	121,488			16,710		15,786
(Benefit) provision for income taxes	(131,096		)	94,849		96,576
Net income	$	3,279		$	193,582	$	175,635


(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.

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, it is not practical to precisely separate our revenues by geographic location. Accordingly, the separation set forth in the table below is based upon internal allocations, which involve certain management estimates and judgments. Revenues in the table are reported based on where the sale is fulfilled; “Other International” revenues are those attributable to all areas located outside of the United States and Canada, as well as Europe, Middle East and Africa.

Summarized information by geographic location as of and for the years ended December 31 follows (in thousands):



	2017		2016		2015
Revenues:
United States and Canada	$	2,037,111	$	1,519,748	$	1,347,676
Europe, Middle East and Africa	850,352		616,721		557,165
Other International	424,031		308,071		258,215
Total revenues	$	3,311,494	$	2,444,540	$	2,163,056

Long-lived assets: (1)
United States and Canada	$	288,735	$	143,921	$	163,933
Europe, Middle East and Africa	84,840		42,326		31,130
Other International	41,674		24,630		16,050
Total long-lived assets	$	415,249	$	210,877	$	211,113


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

Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2017

Valuation and Qualifying Accounts [Abstract]

VALUATION AND QUALIFYING ACCOUNTS

The Company maintains an allowance for losses which is composed of a bad debt allowance and a revenue reserve. Provisions are charged against earnings either as an increase to expense or a reduction in revenues.

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



	Balance at Beginning of Year		Additions Charged to Expense		Additions Charged Against Revenues		Deductions from Reserve			Balance at End of Year
2017:
Allowance for doubtful accounts and returns and allowances	$	7,400	$	16,600	$	5,500	$	(16,800	)	$	12,700
2016:
Allowance for doubtful accounts and returns and allowances	$	6,900	$	4,750	$	4,850	$	(9,100	)	$	7,400
2015:
Allowance for doubtful accounts and returns and allowances	$	6,700	$	3,480	$	5,420	$	(8,700	)	$	6,900

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS On February 6, 2018, the Company announced that it had reached a definitive agreement to sell its CEB Talent Assessment business to Exponent Private Equity, a UK-based private equity firm, for $400.0 million. The CEB Talent Assessment business is a significant portion of the Company's Talent Assessment & Other segment. The agreement comes at the end of a previously announced process to evaluate strategic alternatives for CEB Talent Assessment, formerly SHL, which was acquired by Gartner as part of the CEB acquisition in 2017. The transaction is expected to close in the first half of 2018 and is subject to customary closing conditions. Note 2 — Acquisitions and Divestiture provides additional information.

Business and Significant Accounting Policies (Policies)	12 Months Ended
Business and Significant Accounting Policies (Policies)	Dec. 31, 2017
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 & 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 2017, 2016 and 2015 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, 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 completed acquisitions in each of the three years ended December 31, 2017 and detailed information related to these acquisitions is included in Note 2 — Acquisitions and Divestiture. The Company accounts for acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic No. 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 intangibles also requires management judgment and the evaluation of a number of factors, among them projected cash flows and the likelihood of competition. 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 $158.5 million, $42.6 million and $26.2 million of such charges in 2017, 2016 and 2015, respectively. Included in these directly-related and incremental charges are legal, consulting, retention, severance, and accruals for cash payments subject to the continuing employment of certain key employees of the acquired companies.
Revenue Recognition	Revenue is recognized in accordance with U.S. GAAP and SEC Staff Accounting Bulletin No. 104, Revenue Recognition (“SAB 104”). Revenues are only recognized once all required criteria for recognition have been met. 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. On January 1, 2018, the Company adopted FASB Accounting Standards Update ("ASU") No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09") which requires changes in revenue recognition policies as well as enhanced disclosures. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. Additional information regarding the Company's adoption of ASU No. 2014-09 is provided below in the section titled Accounting standards issued but not yet adopted. The Company’s revenues by significant source are as follows: Research Research revenues are mainly derived from subscription contracts for research products. The related revenues are deferred and recognized ratably over the applicable contract term. Fees derived from assisting organizations in selecting the right business software for their needs are recognized as earned when the leads are provided to vendors. The Company typically enters into subscription contracts for research products for twelve-month periods or longer. The majority of research contracts are billable upon signing, absent special terms granted on a limited basis from time to time. Research contracts are 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 the contract that is billable as a fee receivable at the time the contract is signed with a corresponding amount as deferred revenue, since the contract represents a legally enforceable claim. Consulting 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 on a proportional performance basis, while revenues from time and material engagements are recognized as work is delivered and/or services are provided. Revenues related to contract optimization engagements are contingent in nature and are only recognized upon satisfaction of all conditions related to their payment. Unbilled fees receivable associated with consulting engagements were $66.2 million at December 31, 2017 and $45.7 million at December 31, 2016. Events Events revenues are deferred and recognized upon the completion of the related symposium, conference or exhibition. In addition, the Company defers certain costs directly related to events and expenses these costs in the period during which the related symposium, conference or exhibition occurs. The Company's policy is to defer only those costs, primarily prepaid site and production services costs, which are incremental and are directly attributable to a specific event. Other costs of organizing and producing our events, primarily Company personnel and non-event specific expenses, are expensed in the period incurred. At the end of each fiscal quarter, the Company assesses on an event-by-event basis whether the expected direct costs of producing a scheduled event will exceed the expected revenues. If such costs are expected to exceed revenues, the Company records the expected loss in the period determined. Talent Assessment & Other Talent Assessment & Other revenues arising from knowledge and skill assessment services are recognized depending on the nature of the underlying contract: (i) ratably over the term of the service period; (ii) upon delivery; or (iii) on a proportional performance basis. Revenues from training programs and survey and questionnaire products are primarily recognized upon delivery of the service.
Allowance for losses	The Company maintains an allowance for losses which is composed of a bad debt allowance and a sales reserve. Provisions are charged against earnings, either as a reduction in revenues or an increase to expense. The determination of the allowance for losses 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.
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 the period in which the related revenues are earned. Commission expense is included in SG&A in the Consolidated Statements of Operations.
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 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.
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 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 within our consolidated balance sheets. In assessing the realizability of deferred tax assets, management considers if it is more likely than not that some or all of the deferred tax assets will not be realized. We consider the availability of loss carryforwards, projected reversal of deferred tax liabilities, projected future taxable income, and ongoing prudent and feasible tax planning strategies in making this assessment. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not 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. The cost of these operating leases, including any contractual rent increases, rent concessions, and landlord incentives, are recognized ratably over the life of the related lease agreement. 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 lives of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful lives of the improvement or the remaining term of the related lease. The Company incurs costs to develop internal use software used in our operations, and certain of these costs meeting the criteria outlined in FASB ASC Topic No. 350 are capitalized and amortized over future periods.
Finite-Lived Intangible assets	The Company has finite-lived intangible assets which are amortized against earnings using the straight-line method over their expected useful lives.
Goodwill	Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair value 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.
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, 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 the carrying value can be recovered through undiscounted future operating cash flows. If events or circumstances indicate that the carrying value 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 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.
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 defined benefit plans in accordance with the requirements of FASB ASC Topic No. 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations.
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 in Interest expense in the Consolidated Statements of Operations.
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 income (loss), 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 losses of $(5.5) million, $(0.4) million, and $(2.6) million in 2017, 2016, and 2015, respectively. The Company enters into foreign currency forward exchange contracts to mitigate the effects of adverse fluctuations in foreign currency exchange rates on these transactions. These contracts generally have a short duration and are recorded at fair value with both realized and unrealized gains and losses recorded in Other income, net.
Comprehensive income	The Company reports comprehensive income in a separate statement called the Consolidated Statements of Comprehensive Income, which is included herein.
Fair value disclosures	The Company has a limited number of assets and liabilities that are adjusted to fair value at each balance sheet date.
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, 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 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, 2017 and 2016.
Stock repurchase programs	The Company records the cost to repurchase its own common shares to treasury stock. During 2017, 2016 and 2015, the Company used $41.3 million, $59.0 million, and $509.0 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	Effective January 1, 2016, the Company adopted FASB ASU No. 2016-09, "Improvements to Employee Share-Based Payment Accounting" ("ASU No. 2016-09"). ASU No. 2016-09 mandated certain changes in accounting for stock-based compensation, including a requirement that excess tax benefits or deficiencies resulting from stock-based compensation awards be recognized in income tax expense or benefit subsequent to the date of adopting the new accounting standard. Previously, an entity’s excess tax benefits or deficiencies were recorded in additional paid-in capital. ASU No. 2016-09 also requires that excess tax benefits related to stock-based compensation awards be reported as an operating activity in an entity’s statement of cash flows. Previously, excess tax benefits were reported as financing activities. As permitted by ASU No. 2016-09, the Company elected to apply these changes prospectively, commencing on January 1, 2016. The provisions of ASU No. 2016-09 had no impact on our financial results for periods prior to 2016. If the Company had applied ASU No. 2016-09 to 2015: (i) income tax expense would have declined by $13.9 million; (ii) basic and diluted income per share would have increased by $0.17 and $0.16, respectively; and (iii) cash provided by operating activities would have increased by $13.9 million. ASU No. 2016-09 also 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 optionally 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. The Company did not adopt any significant new accounting standards during 2017. Accounting standards issued but not yet adopted. The FASB has issued accounting standards that have not yet become effective and that may impact the Company’s consolidated financial statements or related disclosures in future periods. These standards and their potential impact are discussed below: Accounting standards effective in 2018 Stock Compensation Award Modifications — In May 2017, the FASB issued 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. ASU No. 2017-09 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-09 will not have a material impact on the Company's consolidated financial statements. Retirement Benefits Cost Presentation — In March 2017, the FASB issued 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, and provides additional guidance on the presentation of net benefit cost in the income statement and clarifies the components eligible for capitalization. ASU No. 2017-07 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-07 will not have a material impact on the Company's consolidated financial statements. Partial Sales of Non-financial Assets — In February 2017, the FASB issued 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 recently established guidance on non-financial asset de-recognition as well as the accounting for partial sales of non-financial assets. It conforms the de-recognition guidance on non-financial assets with the model for revenue transactions. ASU No. 2017-05 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-05 will not have a material impact on the Company's consolidated financial statements. Definition of a Business — In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU No. 2017-01"), which was effective for Gartner on January 1, 2018. ASU No. 2017-01 changes the U.S. GAAP definition of a business which can impact the accounting for asset purchases, acquisitions, goodwill impairment, and other assessments. We have concluded that the adoption of ASU No. 2017-01 will not have a material impact on the Company's consolidated financial statements. Presentation of Restricted Cash — In November 2016, the FASB issued 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 shown on the statement of cash flows. If different, a reconciliation of the cash balances reported in the cash flow statement and the balance sheet would need to be provided along with explanatory information. ASU No. 2016-18 was effective for Gartner on January 1, 2018. The adoption of ASU No. 2016-18 will require the Company to disclose restricted cash and, as a result, will change the presentation of its consolidated statements of cash flows. Income Taxes — In October 2016, the FASB issued 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 and was effective for Gartner on January 1, 2018. Current U.S. GAAP requires deferral of the income tax implications of an intercompany sale of assets until the assets are sold to a third party or recovered through use. Under the new rule, the seller’s tax effects and the buyer’s deferred taxes on post-adoption asset transfers will be immediately recognized upon the sale. On the date of adoption of ASU No. 2016-16 any taxes attributable to pre-2018 intra-entity transfers that were previously deferred will be accelerated and recorded to accumulated earnings as permitted by the transition rules. ASU 2016-16 could have a material impact on our consolidated financial statements in the future depending on the nature, size, and tax consequences of future intra-entity transfers, if any. Statement of Cash Flows — In August 2016, the FASB issued 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. ASU No. 2016-15 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2016-15 will not have a material impact on the Company's consolidated financial statements. Financial Instruments Recognition and Measurement — In January 2016, the FASB issued 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 will be measured at fair value with changes in fair value recognized in net income. ASU No. 2016-01 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2016-01 will not have a material impact on the Company's consolidated financial statements. Revenue Recognition — In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments require changes in revenue recognition policies as well as enhanced disclosures. ASU No. 2014-09 is intended to clarify the principles for recognizing revenue by removing inconsistencies and weaknesses in 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. ASU No. 2014-09 also requires significantly expanded disclosures around the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. An entity may adopt ASU No. 2014-09 using either a full retrospective approach for each prior reporting period presented or a modified retrospective approach (the cumulative effect method). The Company adopted ASU No. 2014-09 on January 1, 2018 using the cumulative effect method of adoption. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. The adoption of the standard does require the Company to reclassify certain immaterial amounts in the Company’s consolidated balance sheet as well as provide the enhanced disclosures required by the standard, both of which will be provided in the Company's Form 10-Q filing for the quarterly period ending March 31, 2018. 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 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 the hedge accounting guidance in current U.S. GAAP. ASU No. 2017-12 is effective for Gartner on January 1, 2019. We are currently evaluating the impact of ASU No. 2017-12 on the Company's consolidated financial statements. Distinguishing Liabilities from Equity — In July 2017, the FASB issued ASU No. 2017-11, "Earnings Per Share, Distinguishing Liabilities from Equity, and Derivatives and Hedging" ("ASU No. 2017-11"). ASU No. 2017-11 is intended to simplify the accounting for financial instruments with characteristics of liabilities and equity. Among the issues addressed are: (i) determining whether an instrument (or embedded feature) is indexed to an entity’s own stock; (ii) distinguishing liabilities from equity for mandatorily redeemable financial instruments of certain nonpublic entities; and (iii) identifying mandatorily redeemable non-controlling interests. ASU No. 2017-11 is effective for Gartner on January 1, 2019. We are currently evaluating the potential impact of ASU No. 2017-11 on the Company's consolidated financial statements. Leases — In February 2016, the FASB issued ASU No. 2016-02, "Leases" ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure for lease arrangements. Currently under U.S. GAAP, lease arrangements that meet certain criteria are considered operating leases and are not recorded on the balance sheet. All of the Company's existing lease arrangements are accounted for as operating leases and are thus not recorded on the Company's balance sheet. ASU No. 2016-02 will significantly change the accounting for leases since a right-of-use ("ROU") model must be used in which the lessee must record a ROU asset and a lease liability on the balance sheet for leases with terms longer than 12 months. Leases will be classified as either finance or operating arrangements, with classification affecting the pattern of expense recognition in the income statement. ASU No. 2016-02 also requires expanded disclosures about leasing arrangements. ASU No. 2016-02 will be effective for Gartner on January 1, 2019. We are currently evaluating the potential impact of ASU No. 2016-02 on our consolidated financial statements. Accounting standards effective in 2020 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 current goodwill impairment test. ASU No. 2017-04 is effective for Gartner on January 1, 2020. We have concluded that the adoption of ASU No. 2017-04 will not 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 also 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. However, since these standards have not yet been issued, the effective dates and potential impact are unknown.

Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

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)	2017			2016
Computer equipment and software	2-7	$	189,015		$	166,385
Furniture and equipment	3-8	67,288			43,137
Leasehold improvements	2-15	175,716			96,603
		$	432,019		$	306,125
Less — accumulated depreciation and amortization		(210,512		)	(184,519		)
Property, equipment, and leasehold improvements, net		$	221,507		$	121,606

Schedule of Changes in Intangible Assets Subject to Amortization

Changes in intangible assets subject to amortization during the two-year period ended December 31, 2017 were as follows (in thousands):



December 31, 2017	Customer Relationships			Software			Content			Other			Total
Gross cost, December 31, 2016	$	63,369		$	16,025		$	3,728		$	33,645		$	116,767
Additions due to acquisitions (1)	1,253,312			180,787			141,707			24,384			1,600,190
Intangibles fully amortized	—			—			(4,227		)	—			(4,227		)
Reclassified as held-for-sale (2)	(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	1,200,316			123,424			104,313			54,929			1,482,982
Accumulated amortization (3)	(92,983		)	(26,344		)	(47,475		)	(24,158		)	(190,960		)
Balance, December 31, 2017	$	1,107,333		$	97,080		$	56,838		$	30,771		$	1,292,022



December 31, 2016	Customer Relationships			Software			Content			Other			Total
Gross cost, December 31, 2015	$	62,860		$	16,219		$	5,450		$	33,474		$	118,003
Additions due to acquisitions	3,677			—			1,948			302			5,927
Intangibles fully amortized	—			(125		)	(162		)	—			(287		)
Foreign currency translation impact	(3,168		)	(69		)	(3,508		)	(131		)	(6,876		)
Gross cost	63,369			16,025			3,728			33,645			116,767
Accumulated amortization (3)	(16,744		)	(8,904		)	(2,033		)	(12,285		)	(39,966		)
Balance, December 31, 2016	$	46,625		$	7,121		$	1,695		$	21,360		$	76,801


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


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


(3)	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.

Schedule of Estimated Future Amortization Expense by Year From Amortizable Intangibles

The estimated future amortization expense by year from finite-lived intangibles is as follows (in thousands):



2018	$	190,442
2019	134,530
2020	128,133
2021	107,715
2022 and thereafter	731,202
	$	1,292,022

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 during the two-year period ended December 31, 2017 (in thousands):



	Research			Consulting			Events			Talent Assessment & Other			Total
Balance, December 31, 2015 (1)	$	575,292		$	98,412		$	41,655		$	—		$	715,359
Additions due to acquisitions	28,465			—			5,843			—			34,308
Foreign currency translation impact	(8,307		)	(1,932		)	(975		)	—			(11,214		)
Balance, December 31, 2016	$	595,450		$	96,480		$	46,523		$	—		$	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		)	1,318			483			20,530			4,044
Balance, December 31, 2017	$	2,619,677		$	97,798		$	187,920		$	81,899		$	2,987,294


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


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


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

Acquisitions and Divestiture (Tables)

12 Months Ended

Dec. 31, 2017

Mergers, Acquisitions And Dispositions Disclosures [Abstract]

Schedule of aggregate purchase price for acquisitions

The following table summarizes the aggregate consideration paid for these acquisitions (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 (5)	$	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 from these businesses and for cash flow reporting purposes, the Company paid a total of $2.63 billion in cash.


(3)	The Company borrowed a total of approximately $2.8 billion in conjunction with the CEB acquisition (see Note 7 — 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.


(5)	The Company may also be required to pay up to an additional $20.8 million in cash for L2 which is contingent on the achievement of certain employment conditions by several key employees. This amount is being recognized as compensation expense over approximately three years.

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

The following table summarizes the preliminary 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; and

(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	)

Summary of amounts related to new building

The following table presents a summary of the activity related to this space for the year ended December 31, 2017 (in thousands):



Liability balance at December 31, 2016	$	—
Charges and adjustments	13,087
Payments	(126		)
Liability balance at December 31, 2017	$	12,961

Principal components of held-for-sale assets and liabilities

The principal components of the held-for-sale assets and liabilities at December 31, 2017 for this business are summarized in the table below (in thousands):



Cash and cash equivalents	$	10,000
Fees receivable, net	50,928
Goodwill	212,994
Intangible assets, net	250,472
Other assets, including property, equipment and leasehold improvements, net	18,571
Total assets held-for-sale	$	542,965

Accounts payable and accrued liabilities	$	32,388
Deferred revenues	61,450
Deferred tax liabilities	47,404
Other liabilities	4,603
Total liabilities held-for-sale	$	145,845

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

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+ Details

Other Assets (Tables)

12 Months Ended

Dec. 31, 2017

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

Schedule of Other Assets

Other assets consist of the following (in thousands):



	December 31,
	2017		2016
Benefit plan-related assets	$	97,525	$	45,958
Non-current deferred tax assets	31,067		27,275
Other	65,150		14,046
Total other assets	$	193,742	$	87,279

Accounts Payable, Accrued, and Other Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Schedule of Accounts Payable and Accrued Liabilities

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



	December 31,
	2017		2016
Accounts payable	$	49,000	$	41,009
Payroll and employee benefits payable	120,278		87,821
Severance and retention bonus payable	44,685		22,425
Bonus payable	162,710		105,549
Commissions payable	108,969		68,273
Taxes payable	46,758		20,378
Other accrued liabilities	134,421		95,316
Total accounts payable and accrued liabilities	$	666,821	$	440,771

Schedule of Other Liabilities

Other liabilities consist of the following (in thousands):



	December 31,
	2017		2016
Non-current deferred revenue	$	16,205	$	11,289
Long-term taxes payable	66,386		19,737
Benefit plan-related liabilities	118,868		67,747
Lease-related matters	115,840		38,042
Non-current deferred tax liabilities	206,338		22,520
Other	54,362		22,482
Total other liabilities	$	577,999	$	181,817

Debt (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Debt

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



	Balance December 31,			Balance December 31,
Description:	2017			2016
2016 Credit Agreement - Term loan A facility (1)	$	1,429,312		$	585,000
2016 Credit Agreement - Term loan B facility (1)	496,250			—
2016 Credit Agreement - Revolving credit facility (1), (2)	595,000			115,000
Senior notes (3)	800,000			—
Other (4)	2,500			2,500
Principal amount outstanding (5), (6)	3,323,062			$	702,500
Less: deferred financing fees (7)	(44,217		)	(8,109		)
Net balance sheet carrying amount	$	3,278,845		$	694,391

(1)


(2)	The Company had $558.0 million of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2017.


(3)	Consists of an $800.0 million principal amount of Senior Notes outstanding. The Senior Notes pay a fixed rate of 5.125% and have an eight year maturity.


(4)	Consists of a $2.5 million State of Connecticut economic development loan with a 3.0% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. Principal payments are deferred for the first five years and the loan may be repaid at any point by the Company without penalty.


(5)	The average annual interest rate on the Company's outstanding debt as of December 31, 2017 was 3.91%, including the effect of its interest rate swaps discussed below.


(6)	The contractual due dates by year on the debt outstanding as of December 31, 2017 are as follows: $80.0 million in 2018; $107.6 million in 2019; $144.7 million in 2020; $42.6 million in 2021; $1.68 billion in 2022; and approximately $1.27 billion thereafter. In January 2018 the Company repaid $255.0 million of outstandings on the revolver which were not contractually due until 2022.


(7)	The deferred financing fees are being amortized to Interest expense, net over the term of the respective debt obligation. 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.

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments under Operating Leases

he future minimum annual cash payments under these operating lease agreements as of December 31, 2017 was as follows (in thousands):



Year ended December 31,
2018	$	129,570
2019	121,543
2020	113,612
2021	106,371
2022	97,225
Thereafter	727,405
Total minimum lease payments (1)	$	1,295,726

(1) Excludes approximately $284.0 million of sublease income.

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

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, 2017:



	Issued Shares	Treasury Stock Shares
Balance at December 31, 2014	156,234,415	68,713,890
Issuances under stock plans	—	(1,003,746	)
Purchases for treasury (1)	—	6,186,101
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


(1)	The Company used a total of $41.3 million, $59.0 million, and $509.0 million in cash for share repurchases in 2017, 2016, and 2015, respectively.

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

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

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	)
Changes during the period:
Change in AOCL/I before reclassifications to income	(1,492		)	—			47,363			45,871
Reclassifications from AOCL/I to income during the period (2), (3)	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

2016



	Interest Rate Swaps			Defined Benefit Pension Plans			Foreign Currency Translation Adjustments			Total
Balance - December 31, 2015	$	(3,079	)	$	(4,832	)	$	(36,491	)	$	(44,402	)
Changes during the period:
Change in AOCL/I before reclassifications to income	(2,902		)	(1,113		)	(5,986		)	(10,001		)
Reclassifications from AOCL/I to income during the period (2), (3)	4,572			148			—			4,720
Other comprehensive income (loss) for the period	1,670			(965		)	(5,986		)	(5,281		)
Balance - December 31, 2016	$	(1,409	)	$	(5,797	)	$	(42,477	)	$	(49,683	)

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

- 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.

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+ Details

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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	2017		2016		2015
Stock appreciation rights	$	5.6	$	5.6	$	5.7
Restricted stock units	72.6		40.4		39.8
Common stock equivalents	0.7		0.7		0.6
Total (1)	$	78.9	$	46.7	$	46.1

Schedule of Stock-based Compensation Expense by Expense Category



Expense category line item	2017		2016		2015
Cost of services and product development	$	25.8	$	21.9	$	20.6
Selling, general and administrative	35.5		24.8		25.5
Acquisition and integration charges (2)	17.6		—		—
Total (1)	$	78.9	$	46.7	$	46.1


(1)	Includes charges of $22.9 million, $19.4 million and $20.1 million during 2017, 2016 and 2015, respectively, for awards to retirement-eligible employees. Those awards vest on an accelerated basis.


(2)	These charges are primarily the result of the acceleration of the vesting of certain restricted stock units related to the CEB acquisition.

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:



	2017		2016		2015
Expected dividend yield (1)	—	%	—	%	—	%
Expected stock price volatility (2)	22	%	22	%	24	%
Risk-free interest rate (3)	1.8	%	1.1	%	1.5	%
Expected life in years (4)	4.53		4.39		4.41


(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).

Stock Appreciation Rights (SARs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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

The following table summarizes changes in SARs outstanding during the year ended December 31, 2017:



	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, 2016	1.3		$	66.22	$	15.77	4.40 years
Granted	0.3		99.07		22.02		6.10 years
Forfeited	(0.1	)	85.28		10.49		n/a
Exercised	(0.3	)	52.72		14.85		n/a
Outstanding at December 31, 2017 (1) (2)	1.2		$	76.73	$	17.35	4.28 years
Vested and exercisable at December 31, 2017 (2)	0.5		$	65.67	$	15.69	3.22 years

n/a = not applicable


(1)	As of December 31, 2017, 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, 2017, the total SARs outstanding had an intrinsic value of $55.0 million. On such date, SARs vested and exercisable had an intrinsic value of $30.2 million.

Restricted Stock Units (RSUs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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, 2017:



	Restricted Stock Units ("RSUs") (in millions)		Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016	1.3		$	73.19
Granted (1) (2)	1.1		105.55
Vested and released	(0.8	)	79.60
Forfeited	(0.1	)	91.03
Outstanding at December 31, 2017 (3) (4)	1.5		$	91.47


(1)	The 1.1 million of RSUs granted during 2017 consisted of 0.2 million of performance-based RSUs awarded to executives and 0.9 million of service-based RSUs awarded to executives, non-executive employees and non-management board members. The 0.2 million of performance-based RSUs represents the target amount of the grant for the year, which is tied to the increase


(2)	Includes 0.6 million of RSUs awarded to employees that joined Gartner as a result of the CEB acquisition.


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


(4)	As of December 31, 2017, the weighted average remaining contractual term of the RSUs outstanding was approximately 1.2 years.

Common Stock Equivalents (CSEs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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

The following table summarizes the changes in CSEs outstanding during the year ended December 31, 2017:



	Common Stock Equivalents ("CSEs")		Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016	107,338		$	20.74
Granted	5,852		120.28
Converted to shares of Common Stock upon grant	(3,177	)	119.10
Outstanding at December 31, 2017	110,013		$	23.19

Computation of Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

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

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



	2017		2016		2015
Numerator:
Net income used for calculating basic and diluted earnings per common share	$	3,279	$	193,582	$	175,635
Denominator: (1)
Weighted average number of common shares used in the calculation of basic earnings per share	88,466		82,571		83,852
Common share equivalents associated with stock-based compensation plans	1,324		1,249		1,204
Shares used in the calculation of diluted earnings per share	89,790		83,820		85,056
Earnings per share: (2)
Basic	$	0.04	$	2.34	$	2.09
Diluted	$	0.04	$	2.31	$	2.06


(1)	The Company repurchased 0.4 million, 0.6 million and 6.2 million shares of its Common Stock in 2017, 2016 and 2015, respectively.


(2)	Both basic and diluted earnings per share for 2017 include a one-time benefit of approximately $0.66 per share related to the Tax Cuts and Jobs Act of 2017. Note 10 — Income Taxes provides information related to the Tax Cuts and Jobs Act of 2017.

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share



	2017		2016		2015
Anti-dilutive common share equivalents as of December 31 (in millions):	0.3		0.2		0.3
Average market price per share of Common Stock during the year	$	116.09	$	92.58	$	86.02

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Components of Income before Income Taxes

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



	2017			2016		2015
U.S.	$	(135,757	)	$	182,178	$	165,848
Non-U.S.	7,940			106,253		106,363
(Loss) income before income taxes	$	(127,817	)	$	288,431	$	272,211

Schedule of Components of Income Tax

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



	2017			2016			2015
Current tax expense:
U.S. federal	$	48,339		$	58,616		$	48,801
State and local	434			11,292			10,300
Foreign	38,602			27,536			23,225
Total current	87,375			97,444			82,326
Deferred tax (benefit) expense:
U.S. federal	(176,046		)	(61		)	(884		)
State and local	(14,363		)	(349		)	(702		)
Foreign	(25,898		)	(1,626		)	1,550
Total deferred	(216,307		)	(2,036		)	(36		)
Total current and deferred	(128,932		)	95,408			82,290
Benefit (expense) relating to interest rate swaps used to increase (decrease) equity	(2,477		)	(1,113		)	893
Benefit from stock transactions with employees used to increase equity	46			52			13,960
Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity	267			502			(567		)
Total tax (benefit) expense	$	(131,096	)	$	94,849		$	96,576

Schedule of Deferred Tax Assets and Liabilities

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



	December 31,
	2017			2016
Accrued liabilities	$	80,557		$	62,439
Loss and credit carryforwards	59,502			7,766
Assets relating to equity compensation	24,874			25,569
Other assets	30,236			6,652
Gross deferred tax assets	195,169			102,426
Property, equipment, and leasehold improvements	(962		)	(11,796		)
Intangible assets	(372,542		)	(43,548		)
Prepaid expenses	(35,126		)	(32,971		)
Other liabilities	(6,584		)	(7,925		)
Gross deferred tax liabilities	(415,214		)	(96,240		)
Valuation allowance	(3,192		)	(1,431		)
Net deferred tax (liabilities) assets	$	(223,237	)	$	4,755

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:



	2017		2016		2015
Statutory tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	3.6		2.4		3.5
Effect of non-U.S. operations	5.9		(6.1	)	(6.9	)
Record (release) reserve for tax contingencies	(2.8	)	3.2		1.7
Law changes	41.8		—		(0.2	)
Excess tax benefits from stock based compensation	11.0		(3.8	)	—
Nondeductible acquisition costs	(7.9	)	2.6		0.8
Nondeductible meals and entertainment costs	(3.5	)	1.1		1.1
Capital loss	13.1		—		—
Record (release) valuation allowance	3.0		(0.2	)	0.5
Other items, net	3.4		(1.3	)	—
Effective tax rate	102.6	%	32.9	%	35.5	%

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):



	2017			2016
Beginning balance	$	37,099		$	25,911
Additions based on tax positions related to the current year	10,883			7,086
Additions for tax positions of prior years	24,299			6,443
Reductions for tax positions of prior years	(10,613		)	(496		)
Reductions for expiration of statutes	(1,368		)	(1,006		)
Settlements	(1,769		)	(544		)
Change in foreign currency exchange rates	1,738			(295		)
Ending balance	$	60,269		$	37,099

Derivatives and Hedging (Tables)

12 Months Ended

Dec. 31, 2017

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 outstanding contracts):

December 31, 2017



Derivative Contract Type	Number of Outstanding Contracts	Notional Amounts		Fair Value Asset (Liability) (3)		Balance Sheet Line Item	Unrealized Gain Recorded in OCI
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

December 31, 2016



Derivative Contract Type	Number of Outstanding Contracts	Notional Amounts		Fair Value Asset (Liability) (3)			Balance Sheet Line Item	Unrealized Loss Recored in OCI
Interest rate swaps (1)	3	$	700,000	$	(2,349	)	Other liabilities	$	(1,409	)
Foreign currency forwards (2)	84	86,946		(320		)	Accrued liabilities	—
Total	87	$	786,946	$	(2,669	)		$	(1,409	)


(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 AOCL/I, net of tax effect (see Note 5 — Debt for 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:	2017			2016		2015
Interest expense (1)	$	7.9		$	7.6	$	8.5
Other (gain) loss, net (2)	(0.8		)	0.3		0.1
Total expense	$	7.1		$	7.9	$	8.6


(1)	Consists of interest 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, 2017

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):



	Fair Value		Fair Value
Description:	December 31, 2017		December 31, 2016
Assets:
Values based on Level 1 inputs:
Deferred compensation plan assets (1)	$	29,108	$	10,252
Total Level 1 inputs	29,108		10,252
Values based on Level 2 inputs:
Deferred compensation plan assets (1)	59,017		27,847
Foreign currency forward contracts (2)	2,053		165
Interest rate swap contracts (3)	3,412		—
Total Level 2 inputs	64,482		28,012
Total Assets	$	93,590	$	38,264
Liabilities:
Values based on Level 2 inputs:
Deferred compensation plan liabilities (1)	$	89,900	$	43,075
Foreign currency forward contracts (2)	1,605		485
Interest rate swap contracts (3)	—		2,349
Senior Notes due 2025 (4)	837,560		—
Total Level 2 inputs	$	929,065	$	45,909
Total Liabilities	$	929,065	$	45,909

(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 the foreign currency forward 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 issued $800.0 million of principal amount fixed-rate Senior Notes due 2025 on March 30, 2017. 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, 2017

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 expense for the years ended December 31 (in thousands):



	2017			2016			2015
Service cost	$	2,820		$	2,780		$	2,620
Interest cost	765			850			790
Expected return on plan assets	(360		)	(375		)	(345		)
Recognition of actuarial loss	350			200			300
Recognition of termination benefits	—			—			85
Total defined benefit pension plan expense (1)	$	3,575		$	3,455		$	3,450


(1)	Pension expense is classified in SG&A in the Consolidated Statements of Operations.

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:



	2017		2016		2015
Weighted average discount rate (1)	1.78	%	1.78	%	2.19	%
Average compensation increase	2.66	%	2.67	%	2.66	%


(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):



	2017			2016			2015
Projected benefit obligation at beginning of year	$	38,400		$	35,870		$	38,115
Service cost	2,820			2,780			2,620
Interest cost	765			850			790
Actuarial loss (gain) due to assumption changes and plan experience	690			1,480			(1,190		)
Additions and contractual termination benefits	(860		)	—			85
Benefits paid (1)	(920		)	(1,640		)	(775		)
Foreign currency impact	4,555			(940		)	(3,775		)
Projected benefit obligation at end of year (2)	$	45,450		$	38,400		$	35,870


(1)	The Company projects the following benefit payments will be made in future years to plan participants: $1.3 million in 2018; $2.2 million in 2019; $1.5 million in 2020, $1.5 million in 2021, $1.6 million in 2022; and $10.5 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:	2017			2016			2015
Projected benefit obligation	$	45,450		$	38,400		$	35,870
Pension plan assets at fair value (1)	(18,475		)	(14,465		)	(13,190		)
Funded status – shortfall (2)	$	26,975		$	23,935		$	22,680



Amounts recorded in the Consolidated Balance Sheets for the plans:
Other liabilities — accrued pension obligation (2)	$	26,975		$	23,935		$	22,680
Stockholders’ equity — deferred actuarial loss (3)	$	(5,861	)	$	(5,797	)	$	(4,832	)

(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, 2017

Segment Reporting [Abstract]

Schedule of Segment Reporting Information by Segment

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



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

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

	Research		Consulting		Events		Talent Assessment & Other	Consolidated
2015 (1)
Revenues	$	1,614,904	$	296,317	$	251,835	—	$	2,163,056
Gross contribution	1,117,534		86,486		130,527		—	1,334,547
Corporate and other expenses								(1,046,550		)
Operating income								$	287,997

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):



	2017			2016		2015
Total segment gross contribution	$	2,000,386		$	1,512,000	$	1,334,547
Costs and expenses:
Cost of services and product development - unallocated (1)	9,090			13,108		10,567
Selling, general and administrative	1,599,004			1,089,184		962,677
Depreciation and amortization	240,171			61,969		47,131
Acquisition and integration charges	158,450			42,598		26,175
Operating (loss) income	(6,329		)	305,141		287,997
Interest expense and other, net	121,488			16,710		15,786
(Benefit) provision for income taxes	(131,096		)	94,849		96,576
Net income	$	3,279		$	193,582	$	175,635


(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

Summarized information by geographic location as of and for the years ended December 31 follows (in thousands):



	2017		2016		2015
Revenues:
United States and Canada	$	2,037,111	$	1,519,748	$	1,347,676
Europe, Middle East and Africa	850,352		616,721		557,165
Other International	424,031		308,071		258,215
Total revenues	$	3,311,494	$	2,444,540	$	2,163,056

Long-lived assets: (1)
United States and Canada	$	288,735	$	143,921	$	163,933
Europe, Middle East and Africa	84,840		42,326		31,130
Other International	41,674		24,630		16,050
Total long-lived assets	$	415,249	$	210,877	$	211,113


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

Valuation and Qualifying Accounts (Tables)

12 Months Ended

Dec. 31, 2017

Valuation and Qualifying Accounts [Abstract]

Summary of Valuation Allowance

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



	Balance at Beginning of Year		Additions Charged to Expense		Additions Charged Against Revenues		Deductions from Reserve			Balance at End of Year
2017:
Allowance for doubtful accounts and returns and allowances	$	7,400	$	16,600	$	5,500	$	(16,800	)	$	12,700
2016:
Allowance for doubtful accounts and returns and allowances	$	6,900	$	4,750	$	4,850	$	(9,100	)	$	7,400
2015:
Allowance for doubtful accounts and returns and allowances	$	6,700	$	3,480	$	5,420	$	(8,700	)	$	6,900

Business and Significant Accounting Policies (Details) $ / shares in Units, enterprise in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) segment country acquisition enterprise $ / shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)
Business and Significant Accounting Policies [Line Items]
Number of enterprises served \| enterprise		12
Number of countries in which entity operates \| country		100
Number of reportable segments \| segment		4
Number of businesses acquired \| acquisition		2
Acquisition and integration charges		$ 158,450,000	$ 42,598,000	$ 26,175,000
Unbilled fees receivable		66,200,000	45,700,000
Stock-based compensation expense		78,943,000	46,661,000	46,149,000
(Benefit) provision for income taxes		$ (131,096,000)	$ 94,849,000	$ 96,576,000
Basic (in Dollars per share) \| $ / shares		$ 0.04	$ 2.34	$ 2.09
Diluted (in Dollars per share) \| $ / shares		$ 0.04	$ 2.31	$ 2.06
Excess tax benefits from share-based compensation, operating activities		$ 0	$ 0	$ 13,860,000
Excess tax benefit from share-based compensation, financing activities		0	0	13,860,000
Adoption of ASU No. 2016-09				(261,000)
Cash and cash equivalents		538,908,000	474,233,000
Cash and cash equivalents including discontinued operations		548,900,000	474,233,000	372,976,000	$ 365,302,000
Rent expense		87,900,000	38,000,000	33,800,000
Depreciation expense		63,897,000	37,172,000	33,789,000
Net capitalized development costs for internal use software		26,900,000	16,600,000
Amortization of capitalized internal software development costs		9,900,000	8,800,000	8,200,000
Amortization of intangibles		176,274,000	24,797,000	13,342,000
Goodwill, impairment loss	$ 0
Pension expense		3,500,000	3,500,000	3,500,000
Long-term debt, gross		3,323,062,000	702,500,000
Foreign currency transaction gain (loss)		(5,500,000)	(400,000)	(2,600,000)
Derivative instruments, gain (loss) recognized in income, net		7,100,000	7,900,000	8,600,000
Payments for purchases of treasury stock		41,272,000	58,961,000	509,049,000
Connecticut Economic Development Program
Business and Significant Accounting Policies [Line Items]
Long-term debt, gross		2,500,000	2,500,000
Principal amount outstanding		2,500,000
Foreign currency exchange contracts
Business and Significant Accounting Policies [Line Items]
Derivative instruments, gain (loss) recognized in income, net		$ 800,000	(300,000)	(100,000)
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
Accumulated Earnings
Business and Significant Accounting Policies [Line Items]
Adoption of ASU No. 2016-09				(261,000)
Accounting Standards Update 2016-09
Business and Significant Accounting Policies [Line Items]
Excess tax benefit from share-based compensation, financing activities			$ 13,900,000
Accounting Standards Update 2016-09 \| Pro Forma
Business and Significant Accounting Policies [Line Items]
(Benefit) provision for income taxes				$ (13,900,000)
Basic (in Dollars per share) \| $ / shares				$ 0.17
Diluted (in Dollars per share) \| $ / shares				$ 0.16
Excess tax benefits from share-based compensation, operating activities				$ 13,900,000
Accounting Standards Update 2016-09 \| Pro Forma \| Accumulated Earnings
Business and Significant Accounting Policies [Line Items]
Adoption of ASU No. 2016-09				$ (300,000)

Business and Significant Accounting Policies (Details) - Property, Equipment and Leasehold Improvements, Less Accumulated Depreciation and Amortization - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 432,019	$ 306,125
Less — accumulated depreciation and amortization	(210,512)	(184,519)
Property, equipment, and leasehold improvements, net	221,507	121,606
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 189,015	166,385
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	$ 67,288	43,137
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	$ 175,716	$ 96,603
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 (Details) - Intangible Assets Subject to Amortization - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-lived Intangible Assets [Roll Forward]
Gross cost	$ 116,767	$ 118,003
Additions due to acquisitions	1,600,190	5,927
Intangibles fully amortized	(4,227)	(287)
Reclassified as held-for-sale	(250,472)
Foreign currency translation impact	20,724	(6,876)
Gross cost	1,482,982	116,767
Accumulated amortization	(190,960)	(39,966)
Finite-lived intangible assets, net	1,292,022	76,801
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost	63,369	62,860
Additions due to acquisitions	1,253,312	3,677
Intangibles fully amortized	0	0
Reclassified as held-for-sale	(140,156)
Foreign currency translation impact	23,791	(3,168)
Gross cost	1,200,316	63,369
Accumulated amortization	(92,983)	(16,744)
Finite-lived intangible assets, net	1,107,333	46,625
Software
Finite-lived Intangible Assets [Roll Forward]
Gross cost	16,025	16,219
Additions due to acquisitions	180,787	0
Intangibles fully amortized	0	(125)
Reclassified as held-for-sale	(69,012)
Foreign currency translation impact	(4,376)	(69)
Gross cost	123,424	16,025
Accumulated amortization	(26,344)	(8,904)
Finite-lived intangible assets, net	97,080	7,121
Content
Finite-lived Intangible Assets [Roll Forward]
Gross cost	3,728	5,450
Additions due to acquisitions	141,707	1,948
Intangibles fully amortized	(4,227)	(162)
Reclassified as held-for-sale	(38,593)
Foreign currency translation impact	1,698	(3,508)
Gross cost	104,313	3,728
Accumulated amortization	(47,475)	(2,033)
Finite-lived intangible assets, net	56,838	1,695
Other
Finite-lived Intangible Assets [Roll Forward]
Gross cost	33,645	33,474
Additions due to acquisitions	24,384	302
Intangibles fully amortized	0	0
Reclassified as held-for-sale	(2,711)
Foreign currency translation impact	(389)	(131)
Gross cost	54,929	33,645
Accumulated amortization	(24,158)	(12,285)
Finite-lived intangible assets, net	$ 30,771	$ 21,360

Business and Significant Accounting Policies (Details) - Estimated Future Amortization Expense by Year from Purchased Intangibles - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2018	$ 190,442
2019	134,530
2020	128,133
2021	107,715
2022 and thereafter	731,202
Finite-lived intangible assets, net	$ 1,292,022	$ 76,801

Business and Significant Accounting Policies (Details) - Changes to the Carrying Amount of Goodwill by Reporting Unit - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning Balance	$ 738,453	$ 715,359
Additions due to acquisition	2,457,791	34,308
Foreign currency translation impact	4,044	(11,214)
Ending Balance	2,987,294	738,453
Not Discontinued Operations
Goodwill [Roll Forward]
Reclassified as held-for-sale	(212,994)
Research
Goodwill [Roll Forward]
Beginning Balance	595,450	575,292
Additions due to acquisition	2,042,514	28,465
Foreign currency translation impact	(18,287)	(8,307)
Ending Balance	2,619,677	595,450
Research \| Not Discontinued Operations
Goodwill [Roll Forward]
Reclassified as held-for-sale	0
Consulting
Goodwill [Roll Forward]
Beginning Balance	96,480	98,412
Additions due to acquisition	0	0
Foreign currency translation impact	1,318	(1,932)
Ending Balance	97,798	96,480
Consulting \| Not Discontinued Operations
Goodwill [Roll Forward]
Reclassified as held-for-sale	0
Events
Goodwill [Roll Forward]
Beginning Balance	46,523	41,655
Additions due to acquisition	140,914	5,843
Foreign currency translation impact	483	(975)
Ending Balance	187,920	46,523
Events \| Not Discontinued Operations
Goodwill [Roll Forward]
Reclassified as held-for-sale	0
Talent Assessment & Other
Goodwill [Roll Forward]
Beginning Balance	0	0
Additions due to acquisition	274,363	0
Foreign currency translation impact	20,530	0
Ending Balance	81,899	$ 0
Talent Assessment & Other \| Not Discontinued Operations
Goodwill [Roll Forward]
Reclassified as held-for-sale	$ (212,994)

Acquisitions and Divestiture (Details) $ in Thousands					3 Months Ended	12 Months Ended
Acquisitions and Divestiture (Details) $ in Thousands	Apr. 05, 2017 USD ($) employee country	Mar. 09, 2017 USD ($) employee	Nov. 09, 2016 USD ($) employee	Jun. 28, 2016 USD ($) employee	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) country	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Percentage of voting interests acquired						100.00%
Consideration transferred, aggregate purchase price						$ 3,653,028
Consideration transferred, cash paid						2,821,903
Fair value of Gartner equity						$ 818,660
Number of countries in which entity operates \| country						100
Net cash paid for acquisition						$ 2,634,809	$ 34,186	$ 196,229
Acquisition and integration charges						158,450	42,598	26,175
Goodwill						2,987,294	738,453	$ 715,359
CEB
Business Acquisition [Line Items]
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, purchase accounting adjustments						$ 32,000
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
Contingent consideration arrangements, maximum value		$ 20,800
Contingent consideration arrangements, maximum value, period of expense recognition		3 years
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
Nubera eBusiness S.L. and Capterra, Inc.
Business Acquisition [Line Items]
Percentage of voting interests acquired								100.00%
Consideration transferred, cash paid								$ 206,900
Net cash paid for acquisition								196,200
Goodwill								138,100
Finite-lived intangible assets								79,600
Liabilities assumed								$ 10,800

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
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, 2017	Apr. 05, 2017	Mar. 09, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets:
Goodwill	$ 2,987,294			$ 738,453	$ 715,359
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, 2017	Dec. 31, 2016
Business Acquisition, Pro Forma Information [Abstract]
Pro forma diluted income (loss) per share (in dollars per share)	$ 0.76	$ (1.84)
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 - Summary of Exited Space Liability (Details) - CEB	12 Months Ended
	Dec. 31, 2017 USD ($)
Liability Related to Exited Space [Roll Forward]
Beginning liability balance	$ 0
Charges and adjustments	13,087,000
Payments	(126,000)
Ending liability balance	$ 12,961,000

Acquisitions and Divestiture - Disposals (Details) - Disposal Group, Held-for-sale, Not Discontinued Operations - CEB Talent Assessment - USD ($) $ in Thousands	9 Months Ended
	Dec. 31, 2017	Feb. 06, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Divestiture, revenue contributed	$ 126,100
Divestiture, operating income (loss)	19,300
Cash and cash equivalents	10,000
Fees receivable, net	50,928
Goodwill	212,994
Intangible assets, net	250,472
Other assets, including property, equipment and leasehold improvements, net	18,571
Total assets held-for-sale	542,965
Accounts payable and accrued liabilities	32,388
Deferred revenues	61,450
Deferred tax liabilities	47,404
Other liabilities	4,603
Total liabilities held-for-sale	$ 145,845
Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of business, consideration		$ 400,000

Other Assets (Details) - Composition of Other Assets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Benefit plan-related assets	$ 97,525	$ 45,958
Non-current deferred tax assets	31,067	27,275
Other	65,150	14,046
Total other assets	$ 193,742	$ 87,279

Accounts Payable, Accrued, and Other Liabilities (Details) - Accounts Payable and Accrued Liabilities - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accounts payable	$ 49,000	$ 41,009
Payroll and employee benefits payable	120,278	87,821
Severance and retention bonus payable	44,685	22,425
Bonus payable	162,710	105,549
Commissions payable	108,969	68,273
Taxes payable	46,758	20,378
Other accrued liabilities	134,421	95,316
Total accounts payable and accrued liabilities	$ 666,821	$ 440,771

Accounts Payable, Accrued, and Other Liabilities (Details) - Other Liabilities - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Non-current deferred revenue	$ 16,205	$ 11,289
Long-term taxes payable	66,386	19,737
Benefit plan-related liabilities	118,868	67,747
Lease-related matters	115,840	38,042
Non-current deferred tax liabilities	206,338	22,520
Other	54,362	22,482
Total other liabilities	$ 577,999	$ 181,817

- Definition

The noncurrent portion of deferred revenue amount as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References + Details

Debt (Details)			1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
Debt (Details)	Apr. 05, 2017 USD ($) amendment installment	Mar. 30, 2017 USD ($)	Jan. 31, 2018 USD ($)	Jun. 30, 2017	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2012
Debt Instrument [Line Items]
Long-term debt, gross						$ 3,323,062,000	$ 702,500,000
Debt instrument, interest rate at period end						3.91%
Long-term Debt, Fiscal Year Maturity [Abstract]
2018						$ 80,000,000
2019						107,600,000
2020						144,700,000
2021						42,600,000
2022						1,680,000,000
Thereafter						1,270,000,000
Payments of deferred financing fees						51,171,000	4,975,000	$ 0
Write off of deferred financing fees					$ 6,100,000
Contract notional amount						2,086,764,000	786,946,000
Interest rate swap
Long-term Debt, Fiscal Year Maturity [Abstract]
Contract notional amount						$ 1,400,000,000
Derivative, term of contract						30 days
Interest rate derivative hedge, asset (liability), net						$ 3,400,000	(2,300,000)
Minimum \| Interest rate swap
Long-term Debt, Fiscal Year Maturity [Abstract]
Derivative, fixed interest rate						1.54%
Maximum \| Interest rate swap
Long-term Debt, Fiscal Year Maturity [Abstract]
Derivative, fixed interest rate						2.13%
CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 2,800,000,000
CEB \| Bridge Loan
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 300,000,000
Debt instrument term	364 days			364 days
Repayments of short-term debt						$ 300,000,000
Term loan
Debt Instrument [Line Items]
Interest rate at period end						3.57%
Debt instrument, interest base rate						1.57%
Debt instrument, interest, additional interest above base rate						2.00%
Long-term debt, gross						$ 1,429,312,000	585,000,000
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	0
Senior notes \| CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 800,000,000
Debt instrument term		8 years
Debt instrument, fixed interest rate		5.125%
Issue price, percent		100.00%
Redeemable percentage of principal amount		40.00%
Senior notes \| CEB \| Redemption period one
Debt Instrument [Line Items]
Redemption price percentage		105.125%
Senior notes \| CEB \| Redemption period two
Debt Instrument [Line Items]
Redemption price percentage		100.00%
Senior notes \| CEB \| Redemption period three
Debt Instrument [Line Items]
Redemption price percentage		101.00%
Connecticut Economic Development Program
Debt Instrument [Line Items]
Debt instrument term									10 years
Debt instrument, fixed interest rate									3.00%
Long-term debt, gross						2,500,000	2,500,000
Principal amount outstanding						$ 2,500,000
Period principal payments term									5 years
Revolving Credit Facility
Debt Instrument [Line Items]
Interest rate at period end						4.07%
Floating eurodollar base rate						1.57%
Additional interest above base rate						2.50%
Line of credit facility, remaining borrowing capacity						$ 558,000,000
Long-term debt, gross						$ 595,000,000	$ 115,000,000
Revolving Credit Facility \| Subsequent Event
Long-term Debt, Fiscal Year Maturity [Abstract]
Repayments of lines of credit			$ 255,000,000
Revolving Credit Facility \| CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 275,000,000
Revolving Credit Facility \| Term B facility
Debt Instrument [Line Items]
Interest rate at period end						2.23%
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%
2016 Credit Facility Agreement \| CEB
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 1,675,000,000
2016 Credit Facility Agreement \| Secured Debt
Debt Instrument [Line Items]
Line of credit facility, frequency of payments in quarterly installments \| installment	16
2016 Credit Facility Agreement \| Secured Debt \| Term loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 1,500,000,000
2016 Credit Facility Agreement \| Secured Debt \| Term loan \| CEB
Debt Instrument [Line Items]
Additional borrowing capacity	$ 900,000,000
2016 Credit Facility Agreement \| Secured Debt \| Term B facility \| CEB
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						500,000,000
Proceeds from issuance of debt	$ 500,000,000
2016 Credit Facility Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 1,200,000,000
Federal Funds rate
Debt Instrument [Line Items]
Additional interest above federal fund rate						0.50%
Term B facility \| Secured Debt \| CEB \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%
Term B facility \| Secured Debt \| CEB \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%

Debt (Details) - Borrowings - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt, gross	$ 3,323,062	$ 702,500
Less: deferred financing fees	(44,217)	(8,109)
Net balance sheet carrying amount	3,278,845	694,391
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	595,000	115,000
Term loan
Debt Instrument [Line Items]
Long-term debt, gross	1,429,312	585,000
Term B facility
Debt Instrument [Line Items]
Long-term debt, gross	496,250	0
Senior notes
Debt Instrument [Line Items]
Long-term debt, gross	800,000	0
Connecticut Economic Development Program
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,500	$ 2,500

Commitments and Contingencies (Details) - Future Minimum Annual Cash Payments Under Non-Cancelable Operating Lease Agreements $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	$ 129,570
2019	121,543
2020	113,612
2021	106,371
2022	97,225
Thereafter	727,405
Total minimum lease payments	1,295,726
Sublease income	$ 284,000

Stockholders' Equity (Details) $ / shares in Units, shares in Millions		12 Months Ended
	Apr. 05, 2017 $ / shares shares	Dec. 31, 2017 USD ($) vote $ / shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 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
Repayments of Long-term Debt		$ 404,438,000	$ 835,000,000	$ 20,000,000
Payments for purchases of treasury stock		41,272,000	$ 58,961,000	$ 509,049,000
Share repurchase program, authorized amount		1,200,000,000
Stock repurchase program, remaining authorized repurchase amount		$ 1,100,000,000
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 (Details) - Summary of Transactions Relating to Common Stock - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock
Common Stock Outstanding Roll Forward [Roll Forward]
Beginning Balance	156,234,415	156,234,415	156,234,415
Issued in connection with the acquisition of CEB	7,367,652
Issuances under stock plans	0	0	0
Purchases for treasury	0	0	0
Ending Balance	163,602,067	156,234,415	156,234,415
Treasury Stock
Common Stock Outstanding Roll Forward [Roll Forward]
Beginning Balance	73,583,172	73,896,245	68,713,890
Issued in connection with the acquisition of CEB	0
Issuances under stock plans	(1,186,150)	(923,696)	(1,003,746)
Purchases for treasury	382,183	610,623	6,186,101
Ending Balance	72,779,205	73,583,172	73,896,245

Stockholders' Equity (Details) - Changes in AOCL/I by Component - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	$ 60,878	$ (132,400)	$ 161,171
Changes during the period:
Change in AOCL/I before reclassifications to income	45,871	(10,001)
Reclassifications from AOCL/I to income during the period	5,320	4,720
Other comprehensive (loss) income, net of tax	51,191	(5,281)	(23,232)
Ending Balance	983,465	60,878	(132,400)
AOCI Attributable to Parent
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(49,683)	(44,402)	(21,170)
Changes during the period:
Other comprehensive (loss) income, net of tax	51,191	(5,281)	(23,232)
Ending Balance	1,508	(49,683)	(44,402)
Interest Rate Swaps
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(1,409)	(3,079)
Changes during the period:
Change in AOCL/I before reclassifications to income	(1,492)	(2,902)
Reclassifications from AOCL/I to income during the period	5,384	4,572
Other comprehensive (loss) income, net of tax	3,892	1,670
Ending Balance	2,483	(1,409)	(3,079)
Defined Benefit Pension Plans
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(5,797)	(4,832)
Changes during the period:
Change in AOCL/I before reclassifications to income	0	(1,113)
Reclassifications from AOCL/I to income during the period	(64)	148
Other comprehensive (loss) income, net of tax	(64)	(965)
Ending Balance	(5,861)	(5,797)	(4,832)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(42,477)	(36,491)
Changes during the period:
Change in AOCL/I before reclassifications to income	47,363	(5,986)
Reclassifications from AOCL/I to income during the period	0	0
Other comprehensive (loss) income, net of tax	47,363	(5,986)
Ending Balance	$ 4,886	$ (42,477)	$ (36,491)

Stock-Based Compensation (Details) - USD ($)	12 Months Ended
Stock-Based Compensation (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	5,700,000
Common stock par value (in Dollars per share)	$ 0.0005	$ 0.0005
Stock-based compensation expense	$ 78,943,000	$ 46,661,000	$ 46,149,000
Total share-based compensation cost not yet recognized	$ 79,900,000
Remaining weighted average service period	2 years 4 months 24 days
Weighted average remaining contractual term	1 year 2 months 12 days
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	800,000
Proceeds from stock grants	$ 11,700,000	9,300,000	7,500,000
Retirement Eligible Employees Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 22,900,000	$ 19,400,000	$ 20,100,000
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average service period	6 years 1 month 6 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	1,300,000
Aggregate intrinsic value of outstanding shares	$ 55,000,000
Aggregate intrinsic value of shares vested and exercisable	$ 30,200,000
Grants during period (in shares)	300,000
Stock Appreciation Rights (SARs) \| 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 (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments number of shares unvested (in shares)	1,500,000	1,300,000
Grants during period (in shares)	1,100,000
Restricted Stock Units (RSUs) \| CEB
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants during period (in shares)	600,000
Restricted Stock Units (RSUs) \| Service-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Grants during period (in shares)	900,000
Restricted Stock Units (RSUs) \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants during period (in shares)	200,000
Performance share, actual yielded performance, percent	186.00%
Restricted Stock Units (RSUs) \| Performance Shares \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance shares, target performance percentage	0.00%
Restricted Stock Units (RSUs) \| Performance Shares \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance shares, target performance percentage	200.00%
Common Stock Equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments number of shares unvested (in shares)	110,013	107,338
Grants during period (in shares)	5,852
Base fee percentage	50.00%

Stock-Based Compensation (Details) - Stock-Based Compensation Expense By Award Type - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 78.9	$ 46.7	$ 46.1
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5.6	5.6	5.7
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	72.6	40.4	39.8
Common stock equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0.7	$ 0.7	$ 0.6

Stock-Based Compensation (Details) - Stock-Based Compensation Expense Recognized In Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 78.9	$ 46.7	$ 46.1
Cost of services and product development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	25.8	21.9	20.6
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	35.5	24.8	25.5
Acquisition and integration charges
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 17.6	$ 0.0	$ 0.0

Stock-Based Compensation (Details) - Summary Of Changes In SARs Outstanding - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Remaining Contractual Term (Years)
Remaining weighted average service period	2 years 4 months 24 days
Stock Appreciation Rights (SARs)
SARs
Outstanding at December 31, 2016 (in shares)	1.3
Granted (in shares)	0.3
Forfeited (in shares)	(0.1)
Exercised (in shares)	(0.3)
Outstanding at December 31, 2017 (in shares)	1.2	1.3
Vested and exercisable at December 31, 2017 (in shares)	0.5
Per Share Weighted Average Exercise Price
Outstanding at December 31, 2016 (in Dollars per share)	$ 66.22
Granted (in Dollars per share)	99.07
Forfeited (in Dollars per share)	85.28
Exercised (in Dollars per share)	52.72
Outstanding at December 31, 2017 (in Dollars per share)	76.73	$ 66.22
Vested and exercisable at December 31, 2017 (in Dollars per share)	65.67
Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016 (in Dollars per share)	15.77
Granted (in Dollars per share)	22.02
Forfeited (in Dollars per share)	10.49
Exercised (in Dollars per share)	14.85
Outstanding at December 31, 2017 (in Dollars per share)	17.35	$ 15.77
Vested and exercisable at December 31, 2017 (in Dollars per share)	$ 15.69
Weighted Average Remaining Contractual Term (Years)
Weighted average remaining contractual terms	4 years 3 months 11 days	4 years 4 months 24 days
Remaining weighted average service period	6 years 1 month 6 days
Weighted average remaining contractual terms vested and exercisable	3 years 2 months 19 days

Stock-Based Compensation (Details) - Weighted-Average Assumptions Used To Determine Fair Value Of SARs Grants On Date Of Grant Using Black-Scholes-Merton Valuation Model - Stock Appreciation Rights (SARs)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected stock price volatility	22.00%	22.00%	24.00%
Risk-free interest rate	1.80%	1.10%	1.50%
Expected life in years	4 years 6 months 11 days	4 years 4 months 21 days	4 years 4 months 28 days

Stock-Based Compensation (Details) - Summary Of Changes In RSUs Outstanding - Restricted Stock Units (RSUs) shares in Millions	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Restricted Stock Units (RSUs)
Outstanding at December 31, 2016 (in shares) \| shares	1.3
Granted (in shares) \| shares	1.1
Vested and released (in shares) \| shares	(0.8)
Forfeited (in shares) \| shares	(0.1)
Outstanding at December 31, 2017 (in shares) \| shares	1.5
Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016 (in Dollars per share) \| $ / shares	$ 73.19
Granted (in Dollars per share) \| $ / shares	105.55
Vested and released (in Dollars per share) \| $ / shares	79.60
Forfeited (in Dollars per share) \| $ / shares	91.03
Outstanding at December 31, 2017 (in Dollars per share) \| $ / shares	$ 91.47

Stock-Based Compensation (Details) - Summary Of Changes In CSEs Outstanding - Common Stock Equivalents (CSEs)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Common Stock Equivalents (CSEs)
Outstanding at December 31, 2016 (in shares) \| shares	107,338
Granted (in shares) \| shares	5,852
Converted to shares of Common Stock upon grant (in shares) \| shares	(3,177)
Outstanding at December 31, 2017 (in shares) \| shares	110,013
Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016 (in Dollars per share) \| $ / shares	$ 20.74
Granted (in Dollars per share) \| $ / shares	120.28
Converted to shares of Common Stock upon grant (in Dollars per share) \| $ / shares	119.10
Outstanding at December 31, 2017 (in Dollars per share) \| $ / shares	$ 23.19

Computation of Earnings Per Share (Details) - Calculations Of Basic And Diluted Earnings Per Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 3,279	$ 193,582	$ 175,635
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	88,466	82,571	83,852
Common share equivalents associated with stock-based compensation plans	1,324	1,249	1,204
Shares used in the calculation of diluted earnings per share	89,790	83,820	85,056
Earnings per share: (2)
Basic (in Dollars per share)	$ 0.04	$ 2.34	$ 2.09
Diluted (in Dollars per share)	$ 0.04	$ 2.31	$ 2.06

Computation of Earnings Per Share (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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)	0.4	0.6	6.2

Computation of Earnings Per Share (Details) - Common Share Equivalents Not Included in the Computation of Diluted EPS - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Anti-dilutive common share equivalents as of December 31 (in shares)	0.3	0.2	0.3
Average market price per share of Common Stock during the year (in dollars per share)	$ 116.09	$ 92.58	$ 86.02

Income Taxes (Details) - Summary of Components of Income Before Income Taxes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
U.S.	$ (135,757)	$ 182,178	$ 165,848
Non-U.S.	7,940	106,253	106,363
(Loss) income before income taxes	$ (127,817)	$ 288,431	$ 272,211

Income Taxes (Details) - Components of Income Tax Expenses - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense:
U.S. federal	$ 48,339	$ 58,616	$ 48,801
State and local	434	11,292	10,300
Foreign	38,602	27,536	23,225
Total current	87,375	97,444	82,326
Deferred tax (benefit) expense:
U.S. federal	(176,046)	(61)	(884)
State and local	(14,363)	(349)	(702)
Foreign	(25,898)	(1,626)	1,550
Total deferred	(216,307)	(2,036)	(36)
Total current and deferred	(128,932)	95,408	82,290
Total tax (benefit) expense	(131,096)	94,849	96,576
Benefit (expense) relating to interest rate swaps used to increase (decrease) equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	(2,477)	(1,113)	893
Benefit from stock transactions with employees used to increase equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	46	52	13,960
Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	$ 267	$ 502	$ (567)

Income Taxes (Details) - Current and Long-Term Deferred Tax Assets and Liabilities - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Accrued liabilities	$ 80,557	$ 62,439
Loss and credit carryforwards	59,502	7,766
Assets relating to equity compensation	24,874	25,569
Other assets	30,236	6,652
Gross deferred tax assets	195,169	102,426
Property, equipment, and leasehold improvements	(962)	(11,796)
Intangible assets	(372,542)	(43,548)
Prepaid expenses	(35,126)	(32,971)
Other liabilities	(6,584)	(7,925)
Gross deferred tax liabilities	(415,214)	(96,240)
Valuation allowance	(3,192)	(1,431)
Net deferred tax (liabilities)	$ 223,237
Net deferred tax assets		$ 4,755

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
Non-current deferred tax assets	$ 31,067	$ 27,275
Non-current deferred tax liabilities	206,338	22,520
Valuation allowance	3,192	1,431
Tax act, provisional tax expense	123,200
Tax act, provisional amount of one-time transition tax liability	63,600
Tax act, increase in income tax expense, transition tax	63,600
Unrecognized tax benefits	60,269	37,099	$ 25,911
Unrecognized tax benefits reductions resulting from settlements with taxing authorities and lapse of applicable statute of limitations	6,300
Unrecognized tax benefits that would impact effective tax rate	57,100
Unrecognized tax benefits that would result adjustments to other tax accounts	3,200
Income tax penalties and interest expense	6,400	4,300
Income tax examination, penalties and interest expense	900	900
Deferred tax liability previously recorded in purchase accounting	12,000
Accumulated undistributed earnings of non-US subsidiaries	194,000
Accounting Standards Update 2016-09
Income Tax [Line Items]
Benefit for income taxes	12,900	10,000
CEB Talent Assessment \| Disposal Group, Held-for-sale, Not Discontinued Operations
Income Tax [Line Items]
Deferred tax asset for CEB talent assessment business	62,900
State and local jurisdiction
Income Tax [Line Items]
Operating loss carryforwards	91,500
Tax credit carryforwards	$ 2,000
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	$ 900
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	$ 19,900
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	$ 70,700
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	$ 16,000
Foreign tax credit carryforwards	59,000
Foreign Tax Authority \| Expire over next twenty years
Income Tax [Line Items]
Operating loss carryforwards	$ 500
Operating loss carryforwards expiration period	20 years
Foreign Tax Authority \| Carried forward indefinitely
Income Tax [Line Items]
Operating loss carryforwards	$ 15,500
Other assets
Income Tax [Line Items]
Non-current deferred tax assets	30,500	27,300
Other liabilities
Income Tax [Line Items]
Non-current deferred tax liabilities	$ 253,700	$ 22,500

Income Taxes (Details) - Differences Between U.S. Federal Statutory Income Tax Rate and Effective Tax Rate on Income Before Income Taxes	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	3.60%	2.40%	3.50%
Effect of non-U.S. operations	5.90%	(6.10%)	(6.90%)
Record (release) reserve for tax contingencies	(2.80%)	3.20%	1.70%
Law changes	0.418	0.000	(0.002)
Excess tax benefits from stock based compensation	11.00%	(3.80%)	(0.00%)
Nondeductible acquisition costs	(7.90%)	2.60%	0.80%
Nondeductible meals and entertainment costs	(3.50%)	1.10%	1.10%
Capital loss	13.10%	0.00%	0.00%
Record (release) valuation allowance	3.00%	(0.20%)	0.50%
Other items, net	3.40%	(1.30%)	0.00%
Effective tax rate	102.60%	32.90%	35.50%

Income Taxes (Details) - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits, Excluding Interest and Penalties - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 37,099	$ 25,911
Additions based on tax positions related to the current year	10,883	7,086
Additions for tax positions of prior years	24,299	6,443
Reductions for tax positions of prior years	(10,613)	(496)
Reductions for expiration of statutes	(1,368)	(1,006)
Settlements	(1,769)	(544)
Change in foreign currency exchange rates	1,738
Decrease in foreign currency exchange rates		(295)
Ending balance	$ 60,269	$ 37,099

Derivatives and Hedging (Details) - Outstanding Derivatives Contracts	12 Months Ended
	Dec. 31, 2017 USD ($) outstanding_contract	Dec. 31, 2016 USD ($) outstanding_contract
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract	142	87
Notional Amounts	$ 2,086,764,000	$ 786,946,000
Fair Value Asset (Liability)	3,860,000	(2,669,000)
Unrealized Gain (Loss) Recorded in OCI	2,483,000	$ (1,409,000)
Interest rate swaps
Derivatives, Fair Value [Line Items]
Notional Amounts	$ 1,400,000,000
Other assets \| Interest rate swaps \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract	5
Notional Amounts	$ 1,400,000,000
Fair Value Asset (Liability)	3,412,000
Unrealized Gain (Loss) Recorded in OCI	$ 2,483,000
Other liabilities \| Interest rate swaps \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract		3
Notional Amounts		$ 700,000,000
Fair Value Asset (Liability)		(2,349,000)
Unrealized Gain (Loss) Recorded in OCI		$ (1,409,000)
Other current assets \| Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract	137
Notional Amounts	$ 686,764,000
Fair Value Asset (Liability)	448,000
Unrealized Gain (Loss) Recorded in OCI	$ 0
Accrued liabilities \| Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract		84
Notional Amounts		$ 86,946,000
Fair Value Asset (Liability)		(320,000)
Unrealized Gain (Loss) Recorded in OCI		$ 0

Derivatives and Hedging (Details) - Derivative Gains And Losses That Have Been Recognized In Condensed Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 7.1	$ 7.9	$ 8.6
Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	7.9	7.6	8.5
Other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ (0.8)	$ 0.3	$ 0.1

Fair Value Disclosures (Details) - USD ($) $ in Millions	Mar. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Money market funds at carrying value		$ 29.1	$ 10.3
Cash surrender value of life insurance		$ 59.0	$ 27.8
Senior notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from issuance of debt	$ 800.0

Fair Value Disclosures (Details) - Assets And Liabilities Measured At Fair Value On Recurring Basis - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Assets measured at fair value on a recurring basis	$ 93,590	$ 38,264
Level 1
Assets:
Assets measured at fair value on a recurring basis	29,108	10,252
Level 1 \| Plan Assets
Assets:
Assets measured at fair value on a recurring basis	29,108	10,252
Level 2
Assets:
Assets measured at fair value on a recurring basis	64,482	28,012
Liabilities:
Liabilities measured at fair value on a recurring basis	929,065	45,909
Level 2 \| Foreign Exchange Forward
Assets:
Assets measured at fair value on a recurring basis	2,053	165
Liabilities:
Liabilities measured at fair value on a recurring basis	1,605	485
Level 2 \| Interest rate swap
Assets:
Assets measured at fair value on a recurring basis	3,412	0
Liabilities:
Liabilities measured at fair value on a recurring basis	0	2,349
Level 2 \| Plan Assets
Assets:
Assets measured at fair value on a recurring basis	59,017	27,847
Level 2 \| Plan Liabilities
Liabilities:
Liabilities measured at fair value on a recurring basis	89,900	43,075
Level 2 \| Debt \| Senior notes
Liabilities:
Liabilities measured at fair value on a recurring basis	$ 837,560	$ 0

Employee Benefits (Details) - USD ($)	12 Months Ended
Employee Benefits (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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	29,800,000	$ 22,900,000	$ 20,000,000
Compensation expense related to deferred compensation plan	400,000	100,000	$ 500,000
Expected future benefit payments, in 2018	1,300,000
Expected future benefit payments, in 2019	2,200,000
Expected future benefit payments, in 2020	1,500,000
Expected future benefit payments, in 2021	1,500,000
Expected future benefit payments, in 2022	1,600,000
Expected future benefit payments in the five years thereafter	$ 10,500,000
Expected long-term return on assets	2.22%
Contributions by employer	$ 2,400,000
Benefits paid to participants under defined benefit plans	$ 1,800,000
Weighted average amortization period	13 years
Future amortization of unrecognized gains losses	$ 300,000
Other assets	9,100,000	7,800,000
Other assets
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation plan assets	88,100,000	38,100,000
Other liabilities
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation liability	$ 89,900,000	$ 43,100,000

Employee Benefits (Details) - Components of Net Periodic Pension Expense - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 2,820	$ 2,780	$ 2,620
Interest cost	765	850	790
Expected return on plan assets	(360)	(375)	(345)
Recognition of actuarial loss	350	200	300
Recognition of termination benefits	0	0	85
Total defined benefit pension expense	$ 3,575	$ 3,455	$ 3,450

Employee Benefits (Details) - Assumptions Used in Computation of Net Periodic Pension Expense	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Weighted-average discount rate	1.78%	1.78%	2.19%
Average compensation increase	2.66%	2.67%	2.66%

Employee Benefits (Details) - Information Related to Changes in Projected Benefit Obligation - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year	$ 38,400	$ 35,870	$ 38,115
Service cost	2,820	2,780	2,620
Interest cost	765	850	790
Actuarial loss (gain) due to assumption changes and plan experience	690	1,480	(1,190)
Additions and contractual termination benefits	(860)	0	85
Benefits paid	(920)	(1,640)	(775)
Foreign currency impact	4,555	(940)	(3,775)
Projected benefit obligation at end of year	$ 45,450	$ 38,400	$ 35,870

Employee Benefits (Details) - Benefit Plans and Related Amounts Recorded in Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligation	$ 45,450	$ 38,400	$ 35,870	$ 38,115
Pension plan assets at fair value	(18,475)	(14,465)	(13,190)
Funded status – shortfall	26,975	23,935	22,680
Amounts recorded in the Consolidated Balance Sheets for the plans:
Other liabilities — accrued pension obligation	26,975	23,935	22,680
Stockholders’ equity — deferred actuarial loss	$ (5,861)	$ (5,797)	$ (4,832)

Segment Information (Details)	12 Months Ended
Segment Information (Details)	Dec. 31, 2017 segment
Segment Reporting Information [Line Items]
Number of reportable segments	4
Maximum
Segment Reporting Information [Line Items]
Percent of target bonus charges allocated to segments	100.00%

Segment Information (Details) - Information About Reportable Segments - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Operating (loss) income	$ (6,329,000)	$ 305,141,000	$ 287,997,000
Operating Segments
Segment Reporting Information [Line Items]
Revenues	3,311,494,000	2,444,540,000	2,163,056,000
Total segment gross contribution	2,000,386,000	1,512,000,000	1,334,547,000
Operating Segments \| Research
Segment Reporting Information [Line Items]
Revenues	2,471,280,000	1,857,001,000	1,614,904,000
Total segment gross contribution	1,653,014,000	1,285,611,000	1,117,534,000
Operating Segments \| Consulting
Segment Reporting Information [Line Items]
Revenues	327,661,000	318,934,000	296,317,000
Total segment gross contribution	93,643,000	89,734,000	86,486,000
Operating Segments \| Events
Segment Reporting Information [Line Items]
Revenues	337,903,000	268,605,000	251,835,000
Total segment gross contribution	163,480,000	136,655,000	130,527,000
Operating Segments \| Talent Assessment & Other
Segment Reporting Information [Line Items]
Revenues	174,650,000	0	0
Total segment gross contribution	90,249,000	0	0
Corporate and Reconciling Items
Segment Reporting Information [Line Items]
Corporate and other expenses	$ (2,006,715,000)	$ (1,206,859,000)	$ (1,046,550,000)

Segment Information (Details) - Reconciliation of Segment Gross Contribution to Net Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Costs and expenses:
Cost of services and product development	$ 1,320,198	$ 945,648	$ 839,076
Selling, general and administrative	1,599,004	1,089,184	962,677
Acquisition and integration charges	158,450	42,598	26,175
Operating (loss) income	(6,329)	305,141	287,997
Interest expense and other, net	121,488	16,710	15,786
(Benefit) provision for income taxes	(131,096)	94,849	96,576
Net income	3,279	193,582	175,635
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	2,000,386	1,512,000	1,334,547
Corporate and Reconciling Items
Costs and expenses:
Cost of services and product development	9,090	13,108	10,567
Selling, general and administrative	1,599,004	1,089,184	962,677
Depreciation and amortization	240,171	61,969	47,131
Acquisition and integration charges	$ 158,450	$ 42,598	$ 26,175

Segment Information (Details) - Summarized Information by Geographic Location - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Revenues	$ 3,311,494	$ 2,444,540	$ 2,163,056
Long-lived assets:
Long-lived assets	415,249	210,877	211,113
United States and Canada
Revenues:
Revenues	2,037,111	1,519,748	1,347,676
Long-lived assets:
Long-lived assets	288,735	143,921	163,933
Europe, Middle East and Africa
Revenues:
Revenues	850,352	616,721	557,165
Long-lived assets:
Long-lived assets	84,840	42,326	31,130
Other International
Revenues:
Revenues	424,031	308,071	258,215
Long-lived assets:
Long-lived assets	$ 41,674	$ 24,630	$ 16,050

- 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://www.xbrl.org/2003/role/presentationRef
-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 2: http://www.xbrl.org/2003/role/presentationRef
-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

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-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 4: http://www.xbrl.org/2003/role/presentationRef
-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 5: http://www.xbrl.org/2003/role/presentationRef
-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 6: http://www.xbrl.org/2003/role/presentationRef
-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 7: http://www.xbrl.org/2003/role/presentationRef
-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 8: http://www.xbrl.org/2003/role/presentationRef
-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

+ Details

Valuation and Qualifying Accounts (Details) - Summarized Activity in Allowances - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 7,400	$ 6,900	$ 6,700
Additions Charged to Expense	16,600	4,750	3,480
Additions Charged Against Revenues	5,500	4,850	5,420
Deductions from Reserve	(16,800)	(9,100)	(8,700)
Balance at End of Year	$ 12,700	$ 7,400	$ 6,900

Subsequent Events (Details) $ in Millions	Feb. 06, 2018 USD ($)
Disposal Group, Held-for-sale, Not Discontinued Operations \| Subsequent Event \| CEB Talent Assessment
Subsequent Event [Line Items]
Sale of business, consideration	$ 400.0