Reconciliation of Revenue and Operating Income by Reportable Segment to Consolidated Results (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Net service revenues	$ 1,164,914	$ 1,063,228	$ 2,249,256	$ 2,086,912
Operating income	123,653	100,794	225,762	190,299
Amortization of intangible assets	224	434	557	867
Interest income, net	(224)	(236)	(462)	(540)
Income before income taxes	123,653	100,596	225,667	189,972
Temporary and consultant staffing
Segment Reporting Information [Line Items]
Net service revenues	911,038	842,069	1,768,608	1,665,491
Operating income	88,756	76,581	166,241	149,761
Permanent placement staffing
Segment Reporting Information [Line Items]
Net service revenues	102,827	90,347	195,452	173,724
Operating income	22,448	15,477	39,723	28,062
Risk consulting and internal audit services
Segment Reporting Information [Line Items]
Net service revenues	151,049	130,812	285,196	247,697
Operating income	$ 12,449	$ 8,736	$ 19,798	$ 12,476