Reconciliation of Revenue and Operating Income (Loss) by Reportable Segment to Consolidated Results (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Net service revenues	$ 1,034,213	$ 1,033,173	$ 1,028,383		$ 1,015,444	$ 973,473	$ 984,668	$ 937,966	$ 880,869	$ 4,111,213	$ 3,776,976	$ 3,175,093
Operating income (loss)										343,446	249,418	115,000
Amortization of intangible assets										398	153	411
Interest income, net										(1,197)	(951)	(579)
Income before income taxes	97,242	94,467	72,272	[1]	80,264	72,161	72,195	61,284	44,576	344,245	250,216	115,168
Temporary and consultant staffing
Segment Reporting Information [Line Items]
Net service revenues										3,324,286	3,050,999	2,568,255
Operating income (loss)										276,826	209,101	108,443
Permanent placement staffing
Segment Reporting Information [Line Items]
Net service revenues										334,198	302,155	221,219
Operating income (loss)										55,745	35,340	17,502
Risk consulting and internal audit services
Segment Reporting Information [Line Items]
Net service revenues										452,729	423,822	385,619
Operating income (loss)										$ 10,875	$ 4,977	$ (10,945)

[1] The decrease in second quarter 2012 income before income taxes, net income, and net income per share was primarily due to a charge related to a litigation settlement disclosed in the Company's July 5, 2012, Form 8-K. The settlement resulted in a non-recurring $19.0 million pre-tax charge to selling, general and administrative expenses and reduced second quarter net income and net income per share by $11.4 million and $0.08 per share, respectively.