Reconciliation of Revenue and Operating Income (Loss) by Reportable Segment to Consolidated Results (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Net service revenues	$ 1,033,173	$ 984,668	$ 3,077,000	$ 2,803,503
Operating income (loss)	94,219	72,086	246,323	177,575
Amortization of intangible assets	100	39	187	118
Interest income, net	(348)	(148)	(867)	(598)
Income before income taxes	94,467	72,195	247,003	178,055
Temporary and consultant staffing
Segment Reporting Information [Line Items]
Net service revenues	831,922	794,722	2,490,587	2,261,773
Operating income (loss)	75,832	61,196	196,654	145,507
Permanent placement staffing
Segment Reporting Information [Line Items]
Net service revenues	81,757	79,064	253,760	227,331
Operating income (loss)	12,538	7,719	44,162	29,461
Risk consulting and internal audit services
Segment Reporting Information [Line Items]
Net service revenues	119,494	110,882	332,653	314,399
Operating income (loss)	$ 5,849	$ 3,171	$ 5,507	$ 2,607