CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Restricted Cash and Cash Equivalents, Current	[1]	$ 36,667	$ 27,044
Current Assets:
Accounts receivable, net of allowance of $9,909 and $8,093 respectively		428,536	386,858
Prepaid expenses and income taxes		18,592	6,331
Workerscompensationreceivable		12,702	14,001
Other current assets		3,026	3,290
Total current assets		499,523	437,524
Property and equipment, net		57,996	56,942
Goodwill		894,095	873,513
Identifiable intangible assets, net		352,766	377,730
Other non-current assets		5,749	6,958
Total assets		1,810,129	1,752,667
Current liabilities:
Accounts payable		6,870	6,266
Accrued payroll and contract professional pay		114,832	111,596
Workers' Compensation Liability, Current		14,777	15,784
Income taxes payable		1,229	1,260
Other current liabilities		29,009	27,593
Total current liabilities		166,717	162,499
Long-term debt		575,213	640,355
Deferred income tax liabilities		69,436	74,282
Other long-term liabilities		7,372	6,592
Total liabilities		818,738	883,728
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred Stock, Value, Issued		0	0
Common Stock, Value, Issued		521	527
Paid-in capital		566,090	562,862
Retained earnings		428,419	315,573
Accumulated other comprehensive loss		(3,639)	(10,023)
Total stockholders’ equity		991,391	868,939
Total liabilities and stockholders’ equity		$ 1,810,129	$ 1,752,667

[1] Includes $2.2 million of restricted cash at December 31, 2017, related to the Company's deferred compensation plan. There was no restricted cash at December 31, 2016. See "Note 12. Stock-Based Compensation and Other Employee Benefit Plans".