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Includes proceeds from stock option exercises and cash usage related to stock withheld to cover taxes on lapsing of stock-based awards. Equity activity related to stock-based awards Activity related to equity-based plans Trade and Other Accounts Receivable, Unbilled Receivables, Policy [Policy Text Block] Professional Employer Organization ("PEO") Unbilled Receivables, Net of Advance Collections Security Exchange Name Revenue from Contract with Customer [Abstract] Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Amount after adjustments of available-for-sale debt securities at cost, maturing after the third fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. 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Funds Held For Clients Money Market Securities And Other Cash Equivalents Fair Value Funds held for clients' money market securities and other restricted cash equivalents, Fair value Revenues [Abstract] Revenue: Amortization of Intangible Assets, Total Amortization of Intangible Assets Amortization expense Receivable [Domain] Receivable [Domain] Other Nonoperating Income (Expense), Total Other Nonoperating Income (Expense) Other Supplemental Information [Text Block] Supplemental Information [Text Block] Supplemental Information Costs To Obtain Contract [Member] Costs To Obtain Contract [Member] Costs To Obtain Contracts [Member] Investment Income, Nonoperating, Total Investment Income, Nonoperating Interest income on corporate investments Entity Central Index Key Entity Central Index Key Other Income and Expenses [Abstract] Capitalized Contract Cost [Axis] Accounting Policies [Abstract] Debt Securities, Available-for-Sale [Line Items] Schedule of Available-for-sale Securities [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Measurement Frequency [Axis] Series B Senior Notes [Member] Series B Senior Notes [Member] Senior Notes, Series B [Member] Advance Collections Current Advance Collections Current Advance collections Fair value of available-for-sale debt securities maturing after the first fiscal year through the third fiscal year following the latest fiscal year. 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Client Fund Obligations Client fund obligations Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Other income/(expense), net Other income/(expense), net Interest Income (Expense), Nonoperating, Net Financial Instrument [Axis] Concentration Risk Benchmark [Axis] Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Noncurrent Long-term corporate investments Stock Repurchase Program Expiration Date Expiration date Authorization repurchase expiration date Debt Securities, Available-for-Sale, Noncurrent Long-term corporate investments Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Securities in an unrealized loss position for less than twelve months, Gross unrealized losses Fair Value Hierarchy and NAV [Domain] Fair Value, Measurements, Fair Value Hierarchy [Domain] Bank Time Deposits [Member] Time Deposits [Member] Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Capitalized Contract Cost, Net, Noncurrent Long-term deferred costs Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Other securities amortized cost. Other Securities Amortized Cost Other, Amortized cost Increase Decrease In Operating Lease Right Of Use Assets and Liabilities, Net Increase Decrease In Operating Lease Right Of Use Assets and Liabilities, Net Net change in operating lease right-of-use assets and liabilities Cover [Abstract] Product and Service [Domain] Product and Service [Domain] Trade Accounts Receivable [Member] Trade Receivables [Member] Supplemental Information [Abstract] Supplemental Information [Abstract] Accounts And Unbilled Receivables [Member] Accounts And Unbilled Receivables [Member] Accounts And Unbilled Receivables [Member] Maximum [Member] Maximum [Member] Unrealized losses on securities, net of tax benefit OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Net Cash Provided by (Used in) Investing Activities Net cash provided by/(used) in investing activities Investments Classified by Contractual Maturity Date [Table Text Block] Amortized Cost and Fair Value of Available-for-Sale Securities by Contractual Maturity Accrued Worksite Employee Compensation And Related Items Accrued Worksite Employee Compensation And Related Items Accrued worksite employee compensation and related items Common Stock, Shares Authorized Common stock, shares authorized Trading Symbol Selling, General and Administrative Expense, Total Selling, General and Administrative Expense Selling, general and administrative expenses Operating Lease, Right-of-Use Asset, Amortization Expense Amortization of operating lease right-of-use assets Notes Payable, Fair Value Disclosure Fair value of long-term borrowings Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income Proceeds from Sale of Property, Plant, and Equipment, Total Proceeds from Sale of Property, Plant, and Equipment Proceeds from sales of property and equipment Accounts Payable, Current, Total Accounts Payable, Current Accounts payable Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax AFS securities, Gross unrealized losses Other securities fair value. Other Securities Fair Value Other, Fair value Common Stock, Par or Stated Value Per Share Common stock, par value Acquisition of businesses, Shares Stock Issued During Period, Shares, Acquisitions Service Revenue [Line Items] Service Revenue [Line Items] Stock Repurchase Program, Authorized Amount Approved repurchase amount Amount authorize to repurchase Acquisition of businesses Stock Issued During Period, Value, Acquisitions Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Deferred revenue, timing of satisfaction Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Weighted-average anti-dilutive common share equivalents Available For Sale, Securities In Unrealized Loss Positions, Percentage Available For Sale, Securities In Unrealized Loss Positions, Percentage Percentage of available-for-sale securities in an unrealized loss position Cash and Cash Equivalents, Fair Value Disclosure Restricted and unrestricted cash equivalents