Consolidated Statements Of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Of Operations [Abstract]
Net service revenues	$ 3,776,976	$ 3,175,093	$ 3,036,547
Direct costs of services, consisting of payroll, payroll taxes, insurance costs and reimbursable expenses	2,287,374	1,981,060	1,932,868
Gross margin	1,489,602	1,194,033	1,103,679
Selling, general and administrative expenses	1,240,184	1,079,033	1,036,899
Amortization of intangible assets	153	411	1,460
Interest income, net	(951)	(579)	(1,443)
Income before income taxes	250,216	115,168	66,763
Provision for income taxes	100,294	49,099	29,500
Net income	149,922	66,069	37,263
Net income available to common stockholders - diluted	$ 147,772	$ 63,729	$ 35,067
Net income per share (Note L):
Basic	$ 1.05	$ 0.45	$ 0.24
Diluted	$ 1.04	$ 0.44	$ 0.24
Shares:
Basic	140,479	142,833	145,912
Diluted	141,790	144,028	146,611
Cash dividends declared per share	$ 0.56	$ 0.52	$ 0.48