Business Segments (Business Segments) (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
Net service revenues	$ 984,668	$ 817,258	$ 2,803,503	$ 2,323,521
Operating income (loss)	72,086	37,162	177,575	71,961
Amortization of intangible assets	39	46	118	362
Interest income, net	(148)	(153)	(598)	(321)
Income before income taxes	72,195	37,269	178,055	71,920
Temporary And Consultant Staffing [Member]
Segment Reporting Information [Line Items]
Net service revenues	794,722	661,178	2,261,773	1,879,661
Operating income (loss)	61,196	31,957	145,507	72,473
Permanent Placement Staffing [Member]
Segment Reporting Information [Line Items]
Net service revenues	79,064	57,177	227,331	161,949
Operating income (loss)	7,719	5,092	29,461	13,748
Risk Consulting And Internal Audit Services [Member]
Segment Reporting Information [Line Items]
Net service revenues	110,882	98,903	314,399	281,911
Operating income (loss)	$ 3,171	$ 113	$ 2,607	$ (14,260)