CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net income	$ 28,737	$ 11,577
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,123	8,746
Stock-based compensation	6,207	7,397
Changes in operating assets and liabilities:
Restricted cash and cash equivalents	(877)	(3,202)
Prepaid income taxes	14,798	6,735
Prepaid expenses and other current assets	1,701	(1,157)
Workers' compensation collateral receivable	(2,872)	(7,688)
Other assets	148	(312)
Accounts payable	(413)	6,111
Accrued corporate wages and other current liabilities	11,903	(2,505)
Workers' compensation loss reserves and other non-current liabilities	8,229	15,205
Worksite employee related assets	242,122	346,563
Worksite employee related liabilities	(241,902)	(347,039)
Net cash provided by operating activities	75,904	40,431
Investing activities
Acquisitions of businesses	0	(300)
Proceeds from maturity of marketable securities	3,625	1,500
Acquisitions of property and equipment	(10,473)	(6,807)
Net cash used in investing activities	(6,848)	(5,607)
Financing activities
Repurchase of common stock	(27,595)	0
Proceeds from issuance of common stock on exercised options	2,099	504
Awards effectively repurchased for required employee withholding taxes	(1,987)	(656)
Repayment of notes and capital leases payable	(9,569)	(5,072)
Net cash used in financing activities	(37,052)	(5,224)
Effect of exchange rate changes on cash and cash equivalents	46	160
Net increase in cash and cash equivalents	32,050	29,760
Cash and cash equivalents at beginning of period	184,004	166,178
Cash and cash equivalents at end of period	216,054	195,938
Supplemental disclosures of cash flow information
Interest paid	4,162	4,083
Income taxes paid (refunded), net	(564)	2,572
Supplemental schedule of noncash investing and financing activities
Payable for purchase of property and equipment	$ 1,971	$ 1,435