CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Cash Flows from Operating Activities:
Net income	$ 157,675	$ 97,201		$ 97,650
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	58,604	62,249		51,569
Provision for Doubtful Accounts	12,050	10,788		10,486
Provision (benefit) for deferred income taxes	(5,140)	12,834		11,549
Allocated Share-based Compensation Expense	24,044	27,024		22,018
Workers' Compensation Provision	2,908	2,693		2,117
Write off of Deferred Debt Issuance Cost	0	0		3,751
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	0	0		(25,703)
Other Noncash Income (Expense)	(6,610)	(5,642)		(7,136)
Changes in operating assets and liabilities:
Accounts receivable	(50,461)	(43,289)		(53,775)
Prepaid expenses and income taxes	(11,861)	6,433		100
Increase (Decrease) in Income Taxes Payable	613	3,346		(7,679)
Accounts payable	315	(2,236)		1,684
Accrued payroll and contract professional pay	1,040	23,556		242
Increase (Decrease) in Workers' Compensation Liabilities	(2,616)	(2,691)		(901)
Payments of earn-outs	0	(4,780)		0
Other	2,665	561		3,800
Net cash provided by operating activities(1)	196,446	199,331	[1]	124,044	[1]
Cash Flows from Investing Activities:
Cash paid for property and equipment	(24,265)	(27,138)		(24,689)
Cash paid for acquisitions, net of cash acquired	(25,940)	0		(552,777)
Proceeds from Divestiture of Businesses, Net of Cash Divested	0	6,000		115,440
Other	88	(846)		496
Net cash used in investing activities	(50,117)	(21,984)		(461,530)
Cash Flows from Financing Activities:
Principal payments of long-term debt	(105,000)	(129,000)		(516,125)
Proceeds from long-term debt	37,000	11,000		875,000
Proceeds from option exercises and employee stock purchase plan	7,755	9,758		6,591
Payment of employment taxes related to release of restricted stock awards	(14,886)	(7,024)		(8,823)
Repurchase of common stock	(60,065)	(41,096)		(1,645)
Debt issuance or amendment costs	(3,273)	(889)		(23,890)
Payments of Merger Related Costs, Financing Activities	0	16,814		0
Net cash provided by (used in) financing activities(1)	(138,469)	(174,065)	[1]	331,108	[1]
Effect of exchange rate changes on cash and cash equivalents	1,763	(107)		(1,467)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	9,623	3,175		(7,845)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	27,044	23,869		31,714
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	36,667	27,044		23,869
Deferred Compensation Plan Assets	2,200
Supplemental Disclosure of Cash Flow Information
Income taxes	55,326	38,190		45,478
Interest	24,074	26,829		22,282
Non-Cash Investing and Financing Activities:
Equity consideration for acquisition	0	0		30,183
Proceeds from Stock Options Exercised	0	0		2,174
Acquisition of property and equipment through accounts payable	2,313	438		989
Unsettled repurchases of common stock	$ 0	$ 1,995		$ 0

[1] Effective January 1, 2017, the Company adopted ASU No. 2016-09, Compensation - Stock Compensation (Topic 718). The Company elected to present retrospectively its gross excess tax benefits as cash flows from operating activities in the consolidated statements of cash flows for all periods presented, which increased cash flows from operating activities and decreased cash flows from financing activities by $3.1 million and $6.6 million for the years ended December 31, 2016 and 2015 respectively, see “Note 2. Accounting Standards Update”.