Business Acquisition [Axis] Business Acquisition [Axis] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Principal amount outstanding Long-Term Debt, Gross Entity Address, Postal Zip Code Entity Address, Postal Zip Code Conferences Events [Member] -- None. No documentation exists for this element. -- 2020 Credit Agreement 2020 Credit Agreement [Member] 2020 Credit Agreement Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Debt Instrument [Axis] Debt Instrument [Axis] Line of credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Fair Value Debt Instrument, Fair Value Disclosure Additional paid-in capital Additional Paid in Capital Types of Financial Instruments [Domain] Financial Instruments [Domain] Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Statistical Measurement [Domain] Statistical Measurement [Domain] Depreciation Depreciation Debt instrument, fixed interest rate Debt Instrument, Interest Rate, Stated Percentage Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance Derivative Instruments, Gain (Loss) [Table Text Block] Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Other current assets Other Current Assets [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Net income Net income Net income used for calculating basic and diluted income per share Net Income (Loss) Attributable to Parent Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Antidilutive securities excluded from computation of (loss) income per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Leases Lessee, Finance Leases [Text Block] Other Other Intangible Assets [Member] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Fees receivable, gross Accounts Receivable, before Allowance for Credit Loss, Current Equity Component [Domain] Equity Component [Domain] Interest expense (income), net Interest Expense [Member] TalentNeuron TalentNeuron [Member] TalentNeuron Total Assets Assets, Fair Value Disclosure Leases Lessee, Operating Leases [Text Block] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Treasury stock, at cost, 84,109,645 and 84,428,513 common shares, respectively Treasury Stock, Common, Value Hedging Designation [Domain] Hedging Designation [Domain] Operating Lease, Liability, Current, Statement of Financial Position [Extensible List] Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration] Derivative Instrument [Axis] Derivative Instrument [Axis] Deferred commissions Other Deferred Costs, Net Goodwill [Line Items] Goodwill [Line Items] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Entity Address, State or Province Entity Address, State or Province Level 1 Fair Value, Inputs, Level 1 [Member] Schedule of Notional Amounts of Outstanding Derivative Positions Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Floating eurodollar base rate Floating Eurodollar Base Rate Floating Euro Dollar Base Rate Award Type [Axis] Award Type [Axis] Debt Instrument, Redemption, Option [Axis] Debt Instrument, Redemption, Option [Axis] Debt Instrument, Redemption, Option Cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Accounts payable and accrued liabilities Operating Lease, Liability, Current Proceeds from sale of divested operation Proceeds from Divestiture of Businesses Costs and expenses: Costs and Expenses [Abstract] Long-term debt, net of deferred financing fees Long-Term Debt, Excluding Current Maturities Total Liabilities Liabilities Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Geographical [Axis] Geographical [Axis] Investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Open Market Purchases, Excluded Open Market Purchases, Excluded [Member] Open Market Purchases, Excluded Percent of outstanding membership interests acquired Business Acquisition, Percentage of Voting Interests Acquired Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Revolving credit facility Revolving Credit Facility [Member] Revenue recognition Revenue from Contract with Customer [Policy Text Block] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Document Type Document Type Transferred at a point in time Transferred at Point in Time [Member] Assets: Assets, Fair Value Disclosure [Abstract] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Segments [Axis] Segments [Axis] Debt Debt Disclosure [Text Block] Other International Other International [Member] -- None. No documentation exists for this element. -- Product and Service [Domain] Product and Service [Domain] Entity Shell Company Entity Shell Company Deferred taxes Deferred Income Tax Expense (Benefit) Deferred revenues Increase (Decrease) in Deferred Revenue Goodwill Disposal Group, Including Discontinued Operation, Goodwill Changes in assets and liabilities, net of acquisitions and divestitures: Increase (Decrease) in Operating Capital, Net of Acquisition [Abstract] -- None. No documentation exists for this element. -- Other Other Long Term Debt [Member] Other Long Term Debt [Member] Financial Instrument [Axis] Financial Instrument [Axis] Unrealized Loss Recorded in AOCL, net of tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax Finite-lived Intangible Assets [Roll Forward] Finite-Lived Intangible Assets [Roll Forward] Consolidation Items [Domain] Consolidation Items [Domain] Schedule for Contract with Customer, Asset and Liability Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Document Period End Date Document Period End Date Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Schedule of the changes in Accumulated Other Comprehensive Loss by component (net of tax) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Total Assets Assets Debt Disclosure [Abstract] Debt Disclosure [Abstract] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs, by Report Line [Axis] Income Statement Location [Axis] Income Statement Location [Axis] Interest rate swaps Interest rate swap contracts Interest Rate Swap [Member] Economic Development Loan 2 Economic Development Loan 2 [Member] Economic Development Loan 2 [Member] Current portion of long-term debt Long-Term Debt, Current Maturities Assets: Contract with Customer, Asset, after Allowance for Credit Loss [Abstract] Deferred revenues Disposal Group, Including Discontinued Operation, Deferred Revenue Cash used in financing activities Net Cash Provided by (Used in) Financing Activities Stock repurchase program, authorized amount Stock Repurchase Program, Authorized Amount Stockholders' Equity Note [Abstract] Stockholders' Equity Note [Abstract] Cost for subleasing activities Operating Lease, Cost, Subleasing Activities Operating Lease, Cost, Subleasing Activities Reclassifications from AOCL to income Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Lease cost Variable Lease, Cost Line of Credit Line of Credit [Member] Gain from sale of divested operation Gain (Loss) on Disposition of Business Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Stockholders’ Equity Stockholders' Equity Attributable to Parent [Abstract] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Segments [Domain] Segments [Domain] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Intangible assets, net Disposal Group, Including Discontinued Operation, Intangible Assets Computation of Earnings Per Share Earnings Per Share [Text Block] Europe, Middle East and Africa Europe Middle East Africa [Member] -- None. No documentation exists for this element. -- Award Type [Domain] Award Type [Domain] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] 2028 Notes Senior Notes Due 2028 [Member] Senior Notes Due 2028 Schedule of amortizable intangible assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Change in AOCL before reclassifications to income Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Derivative Contract [Domain] Derivative Contract [Domain] Entity Registrant Name Entity Registrant Name Connecticut Economic Development Program Connecticut Economic Development Program [Member] -- None. No documentation exists for this element. -- Loss on release of interest rate swap recognized in AOCI AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax Research Research Research Segment [Member] -- None. No documentation exists for this element. -- Accrued liabilities Accrued Liabilities Current [Member] -- None. No documentation exists for this element. -- Foreign currency translation impact Goodwill, Foreign Currency Translation Gain (Loss) Foreign Currency Translation Adjustments Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Customer Relationships Customer Relationships [Member] Entity Address, City or Town Entity Address, City or Town Interest Rate Swaps Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Leases [Abstract] Debt instrument, issue price, percent Debt Instrument, Issue Price, Percentage Debt Instrument, Issue Price, Percentage Intersegment Eliminations Intersegment Eliminations [Member] Principles of consolidation Consolidation, Policy [Policy Text Block] Minimum Minimum [Member] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Entity Emerging Growth Company Entity Emerging Growth Company Common stock, par value (in dollars per share) Common stock par value (in dollars per share) Common Stock, Par or Stated Value Per Share Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Treasury Stock Treasury Stock, Common [Member] Fair Value Disclosures Fair Value Disclosures [Text Block] Trading Symbol Trading Symbol Entity File Number Entity File Number Treasury stock, common shares (in shares) Treasury Stock, Common, Shares Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Non-current deferred revenues recorded in Other liabilities Contract with Customer, Liability, Noncurrent 2027 Finite-Lived Intangible Asset, Expected Amortization, Year Four Restricted stock units Restricted Stock Units (RSUs) [Member] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Variable Rate Component, One Variable Rate Component, One [Member] Variable Rate Component, One Use of estimates Use of Estimates, Policy [Policy Text Block] Revenues Revenues Interest rate swaps – net change in deferred gain or loss Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Accounts payable and accrued and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Income Taxes Income Tax Disclosure [Text Block] Weighted average annual effective rate Debt, Weighted Average Interest Rate Credit Facility [Domain] Credit Facility [Domain] 2029 Notes Senior Notes Due 2029 [Member] Senior Notes Due 2029 Amortization of intangibles Amortization of Intangible Assets Schedule of changes to the carrying amount of goodwill by reporting unit Schedule of Goodwill [Table Text Block] Basic (in dollars per share) Basic income per share (in dollars per share) Earnings Per Share, Basic Net balance sheet carrying amount Debt, Long-Term and Short-Term, Combined Amount Other assets Other Assets [Member] Defined Benefit Pension Plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Total Stockholders’ Equity Beginning balance Ending balance Stockholders' Equity Attributable to Parent Derivatives and Hedging Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Entity Interactive Data Current Entity Interactive Data Current Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Three Accumulated Earnings Retained Earnings [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Other (income) expense, net Other Nonoperating Income (Expense) [Member] Total lease cost, net Lease, Cost Net increase (decrease) in cash and cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Common Stock Common Stock [Member] Schedule of stock-based compensation expense by expense category Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Research Research Revenue [Member] Research Revenue Number of reportable segments Number of Reportable Segments Lease costs Lease, Cost [Table Text Block] Purchases of treasury stock Cash paid for repurchased shares Payments for Repurchase of Common Stock Deferred commissions Increase (Decrease) in Deferred Charges Stock repurchase program, additional authorized amount Stock Repurchase Program, Additional Authorized Amount Stock Repurchase Program, Additional Authorized Amount Number of shares available for grant (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Statement [Table] Statement [Table] Variable Rate Components [Domain] Variable Rate Components [Domain] Variable Rate Components Open Market Purchases Open Market Purchases [Member] Open Market Purchases Renewal term Lessee, Operating Lease, Renewal Term Percentage of principal amount redeemed Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed Document Quarterly Report Document Quarterly Report Current assets: Assets, Current [Abstract] Operating lease liabilities Operating lease liabilities Operating Lease, Liability, Noncurrent Schedule of share repurchase activity Class of Treasury Stock [Table Text Block] Statistical Measurement [Axis] Statistical Measurement [Axis] Number of shares repurchased (in shares) Treasury Stock, Shares, Acquired Leasehold Improvements Leasehold Improvements [Member] Schedule of Disaggregation of Revenue by Reportable Segment Revenue from External Customers by Geographic Areas [Table Text Block] Accumulated earnings Retained Earnings (Accumulated Deficit) Disposal Group Name [Axis] Disposal Group Name [Axis] Debt Instrument Redemption Option One Debt Instrument Redemption Option One [Member] Debt Instrument Redemption Option One Fees receivable, net of allowances of $8,000 and $9,000, respectively Accounts Receivable, after Allowance for Credit Loss, Current Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Equity Components [Axis] Equity Components [Axis] Fair Value, Recurring Fair Value, Recurring [Member] Timing of Transfer of Good or Service [Axis] Timing of Transfer of Good or Service [Axis] Segments Segment Reporting, Policy [Policy Text Block] Option to terminate, term Lessee, Operating Lease, Option to Terminate, Term Lessee, Operating Lease, Option to Terminate, Term Document Fiscal Year Focus Document Fiscal Year Focus Operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Statement [Line Items] Statement [Line Items] Additions to property, equipment and leasehold improvements Payments for Capital Improvements Sale of business, consideration Disposal Group, Including Discontinued Operation, Consideration Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Variable Rate [Domain] Variable Rate [Domain] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Gross cost, beginning balance Gross cost, ending balance Finite-Lived Intangible Assets, Gross Selling, general and administrative Selling, General and Administrative Expense Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Common share repurchases Stock Repurchased During Period, Value Accumulated Other Comprehensive Loss, Net AOCI Attributable to Parent [Member] Document Transition Report Document Transition Report Local Phone Number Local Phone Number Proceeds from event cancellation insurance claims Unusual or Infrequent Item, or Both, Insurance Proceeds Operating income Operating income Total segment gross contribution Operating Income (Loss) Variable Rate Components [Axis] Variable Rate Components [Axis] Variable Rate Components Adoption of new accounting standards New Accounting Pronouncements, Policy [Policy Text Block] Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Goodwill Beginning balance Ending balance Goodwill Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] Total Liabilities Liabilities, Fair Value Disclosure Adjustments to reconcile net income to cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Cash receipts from sublease arrangements Proceeds from Lease Payment, Operating Activity Goodwill and Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Provision for income taxes Less: Provision for income taxes Income Tax Expense (Benefit) Geographical [Domain] Geographical [Domain] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Income Statement [Abstract] Income Statement [Abstract] Additional Paid-In Capital Additional Paid-in Capital [Member] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Document Fiscal Period Focus Document Fiscal Period Focus Other assets Restricted Cash, Noncurrent Unrecognized tax benefits reductions resulting from anticipated closure of audits and the expiration of certain statutes of limitation Unrecognized Tax Benefits, Reductions Resulting from Settlements with Taxing Authorities and Lapse of Applicable Statute of Limitations Unrecognized Tax Benefits, Reductions Resulting from Settlements with Taxing Authorities and Lapse of Applicable Statute of Limitations Cost of services and product development Cost of services and product development - unallocated Cost of Goods and Services Sold Derivative [Line Items] Derivative [Line Items] Diluted (in shares) Shares used in the calculation of diluted income per share (in shares) Weighted Average Number of Shares Outstanding, Diluted Less: deferred financing fees Debt Issuance Costs, Line of Credit Arrangements, Net Fair Value Asset (Liability), Net Derivative Assets (Liabilities), at Fair Value, Net Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Supplemental balance sheet information Assets And Liabilities, Leases [Table Text Block] Assets And Liabilities, Leases [Table Text Block] Accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities, Current Common stock, $0.0005 par value, 250,000,000 shares authorized; 163,602,067 shares issued for both periods Common Stock, Value, Issued Right-of-use Assets Right-of-use Assets [Member] Right-of-use Assets Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Senior Notes Senior Notes [Member] Schedule of Assets and Liabilities Measured to Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Operating Segments Operating Segments [Member] Loss to be reclassified within twelve months Cash Flow Hedge Gain (Loss) to be Reclassified within 12 Months Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Issuances under stock plans Shares Granted, Value, Share-Based Payment Arrangement, after Forfeiture Cash and cash equivalents and restricted cash, beginning of period Cash and cash equivalents and restricted cash, end of period Cash and cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Contingencies Commitments and Contingencies Disclosure [Text Block] Goodwill, accumulated impairment losses Goodwill, Impaired, Accumulated Impairment Loss Current liabilities: Liabilities, Current [Abstract] Foreign currency forwards Foreign currency forward contracts Foreign Exchange Forward [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Common stock, shares issued (in shares) Common Stock, Shares, Issued Liabilities held-for-sale Disposal Group, Including Discontinued Operation, Liabilities, Current Deferred revenues Deferred revenues (current liability) Contract with Customer, Liability, Current Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Report Line [Domain] Income Statement Location [Domain] Income Statement Location [Domain] Transferred over time Transferred over Time [Member] Foreign currency translation impact Finite-Lived Intangible Assets, Foreign Currency Translation Gain (Loss) Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Amendment Flag Amendment Flag Remaining amortization period Finite-Lived Intangible Asset, Useful Life Cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Operating lease cost Operating Lease, Cost Conferences Conferences Conferences [Member] -- None. No documentation exists for this element. -- Aggregate principal amount Debt Instrument, Face Amount Other comprehensive income (loss), net Other Comprehensive Income (Loss), Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Denominator: Denominator: [Abstract] -- None. No documentation exists for this element. -- Proceeds from employee stock purchase plan Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised Acquisitions and Divestiture Mergers, Acquisitions and Dispositions Disclosures [Text Block] Schedule of Segment Reporting Information by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Entity Current Reporting Status Entity Current Reporting Status Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Other assets Other Assets, Noncurrent Depreciation and amortization Depreciation, Depletion and Amortization Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Loss on impairment of lease related assets Loss on impairment of lease related assets, net Operating Lease, Impairment Loss Derivative [Table] Derivative [Table] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Number of contracts Number of Contracts Derivative, Number of Instruments Held Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Basis of presentation Basis of Accounting, Policy [Policy Text Block] Effects of exchange rates on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations Property, equipment and leasehold improvements, net Property, Plant and Equipment, Net Cash paid for amounts included in the measurement of operating lease liabilities Operating Lease, Payments Payments on borrowings Repayments of Long-Term Debt Schedule of estimated future amortization expense by year Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Pension plans – net change in deferred actuarial loss Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Contract liabilities: Contract with Customer, Liability [Abstract] Gain from sale of divested operation Gain from sale of divested operation Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Debt Instrument, Redemption, Period [Domain] Debt Instrument, Redemption, Period [Domain] Fees receivable, allowance Accounts Receivable, Allowance for Credit Loss, Current Carrying Amount Long-Term Debt Other (expense) income, net Other Nonoperating Income (Expense) Balance Sheet Location [Axis] Balance Sheet Location [Axis] Debt Instrument, Redemption, Option [Domain] Debt Instrument, Redemption, Option [Domain] Debt Instrument, Redemption, Option [Domain] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Loss (gain) on de-designated swaps Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Maximum Maximum [Member] Accumulated other comprehensive loss, net Accumulated Other Comprehensive Income (Loss), Net of Tax Percent of target bonus charges allocated to segments Segment Reporting Information, Percent of Target Bonus Charges Allocated to Segments Segment Reporting Information, Percent of Target Bonus Charges Allocated to Segments Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Cash and cash equivalents and restricted cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Total current assets Assets, Current Designated as Hedging Instrument Designated as Hedging Instrument [Member] Revenue recognized previously attributable to deferred revenues Contract with Customer, Liability, Revenue Recognized Business Acquisition [Line Items] Business Acquisition [Line Items] Entity Small Business Entity Small Business Measurement Frequency [Domain] Measurement Frequency [Domain] Equity Stockholders' Equity Note Disclosure [Text Block] Revenues: Revenues [Abstract] Finite-lived intangible assets, net Finite-Lived Intangible Assets, Net Revenue, remaining performance obligation, expected timing of satisfaction, period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period 2030 Notes Senior Notes Due 2030 [Member] Senior Notes Due 2030 Technology-related Computer Software, Intangible Asset [Member] Schedule of Carrying Values and Estimated Fair Values of Debt Instruments Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Sublease income Sublease Income Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset [Domain] Deferred compensation plan assets Plan Assets [Member] -- None. No documentation exists for this element. -- Fees receivable, net Increase (Decrease) in Accounts Receivable Title of 12(b) Security Title of 12(b) Security Business and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Interest expense and other, net Interest Expense and Other Nonoperating Income Interest Expense and Other Nonoperating Income Total costs and expenses Costs and Expenses Class of Treasury Stock [Table] Class of Treasury Stock [Table] Debt Instrument [Line Items] Debt Instrument [Line Items] Business Combination and Asset Acquisition [Abstract] Total operating lease liabilities included in the Condensed Consolidated Balance Sheets Operating Lease, Liability Segment Information Segment Reporting Disclosure [Text Block] Selling, general and administrative Selling, General and Administrative Expenses [Member] Derivative reclassifications Total expense (income), net Derivative, Gain (Loss) on Derivative, Net 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Two Liabilities and Stockholders’ Equity Liabilities and Equity [Abstract] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Weighted average shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Term Loan Facility Term Loan Facility [Member] Term Loan Facility Other assets Increase (Decrease) in Other Operating Assets Hedging Designation [Axis] Hedging Designation [Axis] Entity Filer Category Entity Filer Category Basic (in shares) Weighted average number of common shares used in the calculation of basic income per share (in shares) Weighted Average Number of Shares Outstanding, Basic Liabilities: Liabilities, Fair Value Disclosure [Abstract] Stock-based compensation expense Share-Based Payment Arrangement, Expense Security Exchange Name Security Exchange Name Interest rate swap contracts total notional value Notional Amounts Derivative, Notional Amount Preferred stock, $0.01 par value, 5,000,000 shares authorized; none issued or outstanding Preferred Stock, Value, Issued Assets held-for-sale Disposal Group, Including Discontinued Operation, Assets, Current Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Four Finite-Lived Intangible Asset, Expected Amortization, after Year Four Schedule of Debt Schedule of Debt [Table Text Block] Total revenues Revenue from Contract with Customer, Excluding Assessed Tax Stock appreciation rights Stock Appreciation Rights (SARs) [Member] Consulting Consulting Consulting [Member] -- None. No documentation exists for this element. -- Corporate and Reconciling Items Corporate And Reconciling Items [Member] Corporate And Reconciling Items [Member] Cover page. Cover [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Goodwill impairment Goodwill, Impairment Loss Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Stock-Based Compensation Share-Based Payment Arrangement [Text Block] Schedule of stock-based compensation expense by award type Share-Based Payment Arrangement, Cost by Plan [Table Text Block] Revenue and Related Matters Revenue from Contract with Customer [Text Block] Segment Reporting [Abstract] Segment Reporting [Abstract] Net income per share: Net Income Per Share, Basic And Diluted [Abstract] Net Income Per Share, Basic And Diluted Total Liabilities and Stockholders’ Equity Liabilities and Equity Property, equipment and leasehold improvements, net, Disposal Group, Including Discontinued Operation, Property, Plant and Equipment Debt term Debt Instrument, Term Amortization and write-off of deferred financing fees Amortization of Debt Issuance Costs Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Goodwill [Roll Forward] Goodwill [Roll Forward] Timing of Transfer of Good or Service [Domain] Timing of Transfer of Good or Service [Domain] Stock repurchase program, remaining authorized repurchase amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Additional interest above base rate Debt Instrument, Additional Interest above Base Rate Debt Instrument, Additional Interest above Base Rate Gain on event cancellation insurance claims Gain on event cancellation insurance claims Insured Event, Gain (Loss) Dilutive effect of outstanding awards associated with stock-based compensation plans (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Disposal Group Name [Domain] Disposal Group Name [Domain] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Level 2 Fair Value, Inputs, Level 2 [Member] Schedule of Reconciliation of Segment Gross Contribution to Net Income Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Debt Instrument, Redemption, Period One Debt Instrument, Redemption, Period One [Member] Current Fiscal Year End Date Current Fiscal Year End Date Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Diluted (in dollars per share) Diluted income per share (in dollars per share) Earnings Per Share, Diluted Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Stock-based compensation expense APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Consolidation Items [Axis] Consolidation Items [Axis] Total current liabilities Liabilities, Current Treasury stock, average price paid per share (in dollars per share) Treasury Stock Average Price Paid Per Share Treasury Stock Average Price Paid Per Share. Unrecognized tax benefits Unrecognized Tax Benefits Chicago, Illinois Chicago, Illinois [Member] Chicago, Illinois Share Repurchase Program [Axis] Share Repurchase Program [Axis] Remaining performance obligation, amount Revenue, Remaining Performance Obligation, Amount Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Federal Reserve Board of New York Rate Federal Reserve Board of New York Rate [Member] Federal Reserve Board of New York Rate Common stock equivalents Common Stock Equivalents [Member] -- None. No documentation exists for this element. -- Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Entity Address, Address Line Two Entity Address, Address Line Two Accounts receivable Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net Entity Address, Address Line One Entity Address, Address Line One Contract assets recorded in Prepaid expenses and other current assets Contract with Customer, Asset, before Allowance for Credit Loss Total contract liabilities Contract with Customer, Liability Product and Service [Axis] Product and Service [Axis] Deferred compensation plan liabilities Plan Liabilities [Member] -- None. No documentation exists for this element. -- Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Remaining borrowing capacity Line of Credit Facility, Remaining Borrowing Capacity Interest expense, net Interest Expense Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Credit Facility [Axis] Credit Facility [Axis] Numerator: Numerator: [Abstract] -- None. No documentation exists for this element. -- Entity Tax Identification Number Entity Tax Identification Number Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Fixed interest rate Derivative, Fixed Interest Rate United States and Canada United States And Canada [Member] -- None. No documentation exists for this element. -- Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Revenue from Contract with Customer [Abstract] 2023 (remaining nine months) Finite-Lived Intangible Asset, Expected Amortization, Remainder of Fiscal Year Entity Central Index Key Entity Central Index Key Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Measurement Frequency [Axis] Measurement Frequency [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Purchase price Business Combination, Consideration Transferred City Area Code City Area Code Assets Assets [Abstract] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Retirement Eligible Employees Equity Award Retirement Eligible Employees Equity Award [Member] -- None. No documentation exists for this element. -- Statement of Stockholders' Equity [Abstract] Debt Instrument, Redemption, Period [Axis] Debt Instrument, Redemption, Period [Axis] Acquisition and integration charges Business Combination, Acquisition and Integration Related Costs Business Combination, Acquisition and Integration Related Costs Financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense Variable Rate [Axis] Variable Rate [Axis] Other liabilities Other Liabilities, Noncurrent Reduction in the carrying amount of operating lease right-of-use assets Operating Lease, Right-Of-Use Asset, Reduction In Carrying Amount Operating Lease, Right-Of-Use Asset, Reduction In Carrying Amount Term of contract Derivative, Term of Contract Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] 2024 Finite-Lived Intangible Asset, Expected Amortization, Year One Schedule Of Basic And Diluted Earnings Per Share Calculations Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Right-of-use assets obtained in exchange for new operating lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Contractual annualized interest rate Line of Credit Facility, Interest Rate at Period End Cost of services and product development Cost of Sales [Member]