Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Income Statement [Abstract]
Net service revenues	$ 1,084,342	$ 1,023,684
Direct costs of services, consisting of payroll, payroll taxes, insurance costs and reimbursable expenses	645,847	613,394
Gross margin	438,495	410,290
Selling, general and administrative expenses	336,386	320,785
Amortization of intangible assets	333	433
Interest income, net	(238)	(304)
Income before income taxes	102,014	89,376
Provision for income taxes	40,463	33,513
Net income	61,551	55,863
Net income available to common stockholders-diluted	$ 61,551	$ 55,861
Net income per share (Note I):
Basic	$ 0.45	$ 0.41
Diluted	$ 0.45	$ 0.40
Shares:
Basic	135,333	137,311
Diluted	136,161	138,394
Cash dividends declared per share	$ 0.18	$ 0.16