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Stock Units Granted in 2018 [Member] Class A common stock Common Class A [Member] Beginning of period End of period Total cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Allowance for credit losses for available-for-sale investment securities Debt Securities, Available-for-sale, Allowance for Credit Loss Percent of targeted performance metric Share-based Compensation Arrangements by Share-based Payment Award, Percent Of Award Target Performance Metric Share-based Compensation Arrangements by Share-based Payment Award, Percent Of Award Target Performance Metric Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Income tax payable Taxes Payable, Current Current assets Assets, Current [Abstract] Gross Carrying Value Finite-Lived Intangible Assets, Gross Leases [Abstract] Leases [Abstract] Entity Central Index Key Entity Central Index Key Schedule of Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Amortization expense Capitalized Computer Software, Amortization Security Exchange Name Security Exchange Name Percent of cash bonus payments on initial targets, percent Share-Based Compensation Arrangements By Share-Based Payment Award, Percent Of Cash Bonus Payment On Initial Targets Share-Based Compensation Arrangements By Share-Based Payment Award, Percent Of Cash Bonus Payment On Initial Targets PSUs Granted in 2019 Performance Stock Units Granted in 2019 [Member] Performance Stock Units Granted in 2019 [Member] Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Disposal Group Classification [Domain] Disposal Group Classification [Domain] Exercise of stock options (in shares) Options exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period PSUs Performance Stock Units [Member] Performance Stock Units [Member] Diluted (in shares) Weighted average common shares outstanding; diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Fair value, recurring measurements Fair Value, Recurring [Member] Income received Disposal Group, Including Discontinued Operation, Other Income Income Taxes Income Tax Disclosure [Text Block] Current Fiscal Year End Date Current Fiscal Year End Date Summary of Stock Option Activity Share-based Payment Arrangement, Option, Activity [Table Text Block] Share Repurchase Program Stockholders' Equity Note Disclosure [Text Block] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Working capital adjustment Disposal Group, Including Discontinued Operation, Working Capital Adjustment Disposal Group, Including Discontinued Operation, Working Capital Adjustment Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Performance based cash bonus payment percent Share-based Compensation Arrangements by Share-based Payment Award, Performance Based Cash Bonus Payment, Percent Share-based Compensation Arrangements by Share-based Payment Award, Performance Based Cash Bonus Payment, Percent Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Cash from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Total current liabilities Liabilities, Current Tax withholding for net share settlement Payment, Tax Withholding, Share-based Payment Arrangement Class of Stock [Domain] Class of Stock [Domain] Money market funds Money Market Funds [Member] Loss Contingencies [Table] Loss Contingencies [Table] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Accrued commissions Accrued Sales Commission, Current Document Information [Line Items] Document Information [Line Items] Title of 12(b) Security Title of 12(b) Security Statement [Table] Statement [Table] Recent Accounting Pronouncements Adopted in 2020 and 2021 New Accounting Pronouncements, Policy [Policy Text Block] Prepaid Expenses and Other Current Assets Prepaid Expenses and Other Current Assets [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Cover [Abstract] Cover [Abstract] Database Database [Member] Database [Member] Net Carrying Value Finite-Lived Intangible Assets, Net Goodwill Goodwill Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Four Lessee, Operating Lease, Liability, to be Paid, after Year Four Nature of Business Nature of Operations [Text Block] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Due in one year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Operating lease cost Operating Lease, Cost Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Depreciation and amortization Depreciation, Depletion and Amortization, Excluding Amortization of Financing Costs Depreciation, Depletion and Amortization, Excluding Amortization of Financing Costs Executive Executive Officer [Member] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table]