CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities:
Net income	$ 111,825	$ 90,344
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	71,298	43,493
Stock-based compensation	22,380	17,943
Provision for accounts receivable allowances	2,133	9,216
Workers’ compensation provision	2,459	2,383
Other	13,046	5,967
Changes in operating assets and liabilities:
Accounts receivable	(47,819)	(51,936)
Prepaid expenses and income taxes	12,482	(958)
Accounts payable	9,892	(135)
Accrued payroll and contract professional pay	26,942	14,291
Income taxes payable	6,849	13,426
Workers’ compensation loss reserves	(2,287)	(1,952)
Other	(5,639)	(3,895)
Net Cash Provided by Operating Activities	223,561	138,187
Cash Flows from Investing Activities:
Cash paid for property and equipment	(22,093)	(18,038)
Cash paid for acquisitions, net of cash acquired	(760,253)	(25,828)
Other	(180)	0
Net cash used in investing activities	(782,526)	(43,866)
Cash Flows from Financing Activities:
Principal payments of long-term debt	(231,000)	(69,500)
Proceeds from long-term debt	822,000	37,000
Debt issuance and amendment costs	(22,450)	(3,273)
Proceeds from option exercises and employee stock purchase plan	9,342	7,690
Payment of employment taxes related to release of restricted stock awards	(4,402)	(7,785)
Repurchase of common stock	0	(58,949)
Other	(9,473)	0
Net Cash provided by (used in) Financing Activities	564,017	(94,817)
Effect of exchange rate changes on cash and cash equivalents	(831)	1,429
Net Increase (Decrease) in Cash and Cash Equivalents	4,221	933
Cash and Cash Equivalents at Beginning of Year	36,667	27,044
Cash and Cash Equivalents at End of Period	40,888	27,977
Supplemental Disclosure of Cash Flow Information:
Income taxes	10,184	37,716
Interest	37,828	18,980
Supplemental Disclosure of Non-Cash Transactions:
Unpaid portion of additions to property and equipment	1,676	2,063
Unsettled repurchases of common stock	$ 0	$ 1,074