CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities
Net income	$ 91	$ 63
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15	18
Noncash lease expense	4	0
Stock based compensation	9	9
Changes in operating assets and liabilities:
Accounts receivable, net	0	1
Unbilled revenue, net	(95)	(9)
Prepaid expenses, net	(3)	(12)
Accounts payable and other current liabilities	29	9
Client deposits	(6)	(19)
Accrued wages	38	17
Accrued health insurance costs, net	(2)	0
Accrued workers' compensation costs, net	3	(2)
Payroll taxes payable and other payroll withholdings	(334)	(180)
Operating lease liabilities	(5)	(4)
Other assets	(28)	(30)
Other liabilities	2	(3)
Net cash used in operating activities	(282)	(142)
Investing activities
Purchases of marketable securities	(155)	(30)
Proceeds from sales and maturities of marketable securities	67	31
Acquisitions of property and equipment	(6)	(12)
Net cash used in investing activities	(94)	(11)
Financing activities
Repurchase of common stock	(40)	(38)
Proceeds from issuance of common stock	0	1
Awards effectively repurchased for required employee withholding taxes	(3)	(4)
Proceeds from revolving credit agreement borrowings	234	0
Repayment of debt	(6)	(6)
Net cash provided by (used in) financing activities	185	(47)
Net decrease in cash and cash equivalents, unrestricted and restricted	(191)	(200)
Cash and cash equivalents, unrestricted and restricted:
Beginning of period	1,456	1,349
End of period	1,265	1,149
Supplemental disclosures of cash flow information
Interest paid	3	4
Income taxes paid, net	1	1
Supplemental schedule of noncash investing and financing activities
Payable for purchase of property and equipment	$ 1	$ 5