CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Operating activities
Net income	$ 308	$ 307
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangible assets	53	48
Amortization of deferred costs	31	26
Amortization of ROU asset, lease modification, impairment, and abandonment	5	15
Stock based compensation	43	46
Deferred income taxes	(2)	1
Provision for doubtful accounts	2	1
Losses and impairment on investments	0	18
Losses from disposition of assets	0	3
Other	1	0
Changes in operating assets and liabilities:
Accounts receivable, net	(4)	10
Unbilled revenue, net	(29)	(38)
Prepaid expenses, net	(4)	3
Other assets	(44)	(30)
Other payroll assets	(104)	(56)
Accounts payable and other liabilities	9	5
Client deposits and other client liabilities	(33)	(43)
Accrued wages	21	40
Accrued health insurance costs, net	9	(10)
Accrued workers' compensation costs, net	(9)	(5)
Payroll taxes payable and other payroll withholdings	(283)	(252)
Operating lease liabilities	(13)	(13)
Net cash provided by (used in) operating activities	(43)	76
Investing activities
Purchases of marketable securities	(226)	(337)
Proceeds from sale and maturity of marketable securities	223	390
Acquisitions of property and equipment	(54)	(39)
Acquisition of subsidiary, net of cash acquired	0	(219)
Net cash used in investing activities	(57)	(205)
Financing activities
Repurchase of common stock	(1,109)	(383)
Proceeds from issuance of common stock	9	6
Proceeds from issuance of 2031 Notes	400	0
Awards effectively repurchased for required employee withholding taxes	(14)	(15)
Proceeds from revolving credit agreement borrowings	695	0
Payment of long-term financing fees and debt issuance costs	(9)
Repayment of borrowings under revolving credit facility	(495)	0
Net cash used in financing activities	(523)	(392)
Net decrease in cash and cash equivalents, unrestricted and restricted	(623)	(521)
Cash and cash equivalents, unrestricted and restricted:
Beginning of period	1,537	1,738
End of period	914	1,217
Supplemental disclosures of cash flow information
Interest paid	21	18
Income taxes paid, net	89	60
Supplemental schedule of noncash investing and financing activities
Payable for purchase of property and equipment	2	7
Acquisitions of subsidiaries paid in stock	$ 0	$ 4