Business Segments (Business Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Segment Reporting Information [Line Items]
Net service revenues	$ 1,015,444	$ 880,869
Operating income (loss)	80,065	44,403
Amortization of intangible assets	35	39
Interest income, net	(234)	(212)
Income before income taxes	80,264	44,576
Temporary And Consultant Staffing [Member]
Segment Reporting Information [Line Items]
Net service revenues	829,657	714,682
Operating income (loss)	69,154	38,070
Permanent Placement Staffing [Member]
Segment Reporting Information [Line Items]
Net service revenues	82,862	67,604
Operating income (loss)	13,266	7,867
Risk Consulting And Internal Audit Services [Member]
Segment Reporting Information [Line Items]
Net service revenues	102,925	98,583
Operating income (loss)	$ (2,355)	$ (1,534)