Reconciliation of Revenue and Operating Income (Loss) by Reportable Segment to Consolidated Results (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Net service revenues	$ 1,063,228	$ 1,028,383	$ 2,086,912	$ 2,043,827
Operating income (loss)	100,794	72,039	190,299	152,104
Amortization of intangible assets	434	52	867	87
Interest income, net	(236)	(285)	(540)	(519)
Income before income taxes	100,596	72,272	189,972	152,536
Operating Segments
Segment Reporting Information [Line Items]
Amortization of intangible assets	434	52	867	87
Interest income, net	(236)	(285)	(540)	(519)
Operating Segments | Temporary and consultant staffing
Segment Reporting Information [Line Items]
Net service revenues	842,069	829,008	1,665,491	1,658,665
Operating income (loss)	76,581	51,668	149,761	120,822
Operating Segments | Permanent placement staffing
Segment Reporting Information [Line Items]
Net service revenues	90,347	89,141	173,724	172,003
Operating income (loss)	15,477	18,358	28,062	31,624
Operating Segments | Risk consulting and internal audit services
Segment Reporting Information [Line Items]
Net service revenues	130,812	110,234	247,697	213,159
Operating income (loss)	$ 8,736	$ 2,013	$ 12,476	$ (342)