Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net service revenues	$ 1,224,308	$ 1,075,119	$ 3,473,564	$ 3,162,031
Direct costs of services, consisting of payroll, payroll taxes, insurance costs and reimbursable expenses	719,088	637,641	2,051,405	1,882,155
Gross margin	505,220	437,478	1,422,159	1,279,876
Selling, general and administrative expenses	366,967	333,565	1,058,144	985,664
Amortization of intangible assets	0	433	557	1,300
Interest income, net	(108)	(233)	(570)	(773)
Income before income taxes	138,361	103,713	364,028	293,685
Provision for income taxes	53,177	37,355	142,153	108,375
Net income	85,184	66,358	221,875	185,310
Net income available to common stockholders—diluted	$ 85,184	$ 66,358	$ 221,875	$ 185,307
Net income per share:
Basic (in usd per share)	$ 0.64	$ 0.49	$ 1.65	$ 1.36
Diluted (in usd per share)	$ 0.63	$ 0.48	$ 1.63	$ 1.35
Shares:
Basic (in shares)	134,054	135,727	134,690	136,469
Diluted (in shares)	135,366	137,241	135,740	137,759
Cash dividends declared per share	$ 0.18	$ 0.16	$ 0.54	$ 0.48