| Dec 31, 2014 | Dec 31, 2015 | Dec 31, 2016 | Dec 31, 2017 | Dec 31, 2018 | Dec 31, 2019 | Dec 31, 2020 | Dec 31, 2021 | Dec 31, 2022 | Dec 31, 2023 | Dec 31, 2024 |
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| Net income | 15 | 32 | 61 | 178 | 192 | 212 | 272 | 338 | 355 | 375 | 173 |
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| Other Depreciation and Amortization | - | - | - | - | - | 57 | 67 | 82 | 101 | 72 | 75 |
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| Amortization of deferred costs | - | - | - | - | - | - | - | - | - | 40 | 44 |
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| Operating Lease, Right-of-Use Asset, Periodic Reduction | - | - | - | - | - | - | - | - | 25 | 9 | 11 |
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| Stock based compensation | 11 | 18 | 26 | 32 | 44 | 41 | 43 | 50 | 62 | 59 | 65 |
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| Accretion of discount rate on lease liabilities | - | - | - | - | - | - | -2 | -2 | -2 | -2 | -2 |
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| Provision for doubtful accounts | - | - | - | - | - | - | - | - | 2 | 3 | 2 |
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| Deferred income taxes | - | - | - | - | - | - | - | -9 | -22 | 5 | -2 |
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| Losses from disposition of assets | - | - | - | - | - | - | - | - | -6 | -1 | - |
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| Losses and impairment on investments | - | - | - | - | - | - | - | - | -18 | -1 | 1 |
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| Goodwill and Intangible Asset Impairment | - | - | - | - | - | - | - | - | - | - | 25 |
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| Accounts receivable, net | - | - | - | - | -10 | -5 | 7 | -3 | - | 2 | 2 |
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| Prepaid expenses, net | - | - | - | - | - | 5 | 12 | 5 | 2 | -4 | 18 |
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| Other payroll assets | - | - | - | - | - | - | - | - | 72 | 259 | -3 |
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| Accounts payable and other current liabilities | - | - | - | - | - | -15 | 19 | 33 | -13 | -8 | -7 |
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| Client deposits and other client liabilities | - | - | - | - | - | - | 87 | -37 | 9 | -40 | -10 |
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| Accrued wages | - | - | - | - | 23 | 40 | -82 | 60 | 65 | 77 | -5 |
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| Accrued health insurance costs, net | - | - | - | - | -16 | 32 | 5 | 2 | - | 1 | -2 |
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| Accrued workers' compensation costs, net | - | - | - | - | -7 | -20 | -9 | -7 | -8 | -12 | -11 |
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| Payroll taxes payable and other payroll withholdings | - | - | - | - | - | 172 | 194 | -166 | 158 | 351 | -3 |
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| Operating lease liabilities | - | - | - | - | - | - | - | - | - | - | -15 |
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| Other assets | -8 | 15 | -0 | -4 | 64 | 34 | 38 | 50 | 55 | 38 | 52 |
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| Other liabilities | - | - | - | - | -1 | -12 | 11 | -2 | -2 | -7 | 7 |
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| Net cash provided by operating activities | - | - | 145 | 253 | -104 | 471 | 546 | 218 | 562 | 545 | 279 |
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| Purchases of marketable securities | - | - | 15 | - | - | 302 | 327 | 444 | 410 | 276 | 190 |
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| Proceeds from sale and maturity of marketable securities | - | - | 28 | 14 | 101 | 159 | 224 | 349 | 469 | 286 | 421 |
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| Acquisitions of property and equipment and projects in process | 21 | 19 | 40 | 38 | 43 | 45 | 36 | 40 | 56 | 75 | 78 |
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| Acquisitions of subsidiaries, net of cash acquired | - | 5 | 0 | - | 258 | - | - | - | 229 | - | - |
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| Other Investments | - | - | - | - | - | - | - | - | - | 5 | - |
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| Net cash provided by (used in) investing activities | - | - | -27 | -24 | -200 | -188 | -151 | -135 | -226 | -70 | 153 |
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| Change in WSE and TriNet Trust related assets and liabilities, net | - | - | - | - | - | - | - | - | - | - | -139 |
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| Repurchase of common stock | 16 | 48 | 72 | 44 | 61 | 140 | 178 | 94 | 523 | 1,122 | 183 |
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| Proceeds from issuance of common stock | 218 | - | - | - | 14 | 11 | 10 | 11 | 11 | 15 | 12 |
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| Payment of long-term financing costs and debt issuance costs | - | - | - | - | - | - | - | - | - | 9 | - |
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| Proceeds from Notes Payable | - | - | 58 | - | 210 | - | - | 500 | - | - | - |
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| Proceeds from Lines of Credit | - | - | - | - | - | - | 234 | - | - | 695 | - |
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| Repayment of borrowings under revolving credit agreement | - | - | - | - | - | - | 234 | - | - | 495 | 110 |
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| Awards effectively repurchased for required employee withholding taxes | - | - | - | - | - | 25 | 18 | 26 | 24 | 30 | 28 |
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| Dividends paid | - | - | - | - | - | - | - | - | - | - | 37 |
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| Net cash used in financing activities | - | - | -99 | -77 | -85 | -176 | -208 | 12 | -536 | -546 | -207 |
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| Effect of exchange rate changes on cash and cash equivalents | - | - | - | - | - | - | - | - | -1 | - | - |
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| Net increase (decrease) in cash and cash equivalents, unrestricted and restricted | - | - | - | - | -389 | 107 | 187 | 95 | -201 | -71 | 225 |
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| Interest paid | - | - | - | - | - | 19 | 16 | 12 | 18 | 25 | 59 |
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| Income taxes paid, net | -4 | 2 | 39 | 2 | 49 | 62 | 123 | 129 | 128 | 114 | 76 |
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| Payable for purchase of property and equipment | 1 | 0 | 1 | 2 | 3 | 2 | 2 | - | 6 | 4 | 2 |
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| Acquisitions of subsidiaries paid in stock | - | - | - | - | - | - | - | - | 17 | - | - |
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