Reconciliation of Revenue and Operating Income by Reportable Segment to Consolidated Results (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Net service revenues	$ 1,075,119	$ 1,033,173	$ 3,162,031	$ 3,077,000
Operating income	103,913	94,219	294,212	246,323
Amortization of intangible assets	433	100	1,300	187
Interest income, net	(233)	(348)	(773)	(867)
Income before income taxes	103,713	94,467	293,685	247,003
Temporary and consultant staffing
Segment Reporting Information [Line Items]
Net service revenues	847,886	831,922	2,513,377	2,490,587
Operating income	76,532	75,832	226,293	196,654
Permanent placement staffing
Segment Reporting Information [Line Items]
Net service revenues	88,222	81,757	261,946	253,760
Operating income	13,691	12,538	41,753	44,162
Risk consulting and internal audit services
Segment Reporting Information [Line Items]
Net service revenues	139,011	119,494	386,708	332,653
Operating income	$ 13,690	$ 5,849	$ 26,166	$ 5,507