Revenue and Long-Lived Assets by Geographic Location (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
Schedule Of Geographical 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
Assets, long-lived	107,680				107,972				107,680	107,972	103,651
Domestic
Schedule Of Geographical Information [Line Items]
Net service revenues									3,022,274	2,655,443	2,263,316
Assets, long-lived	86,239				87,146				86,239	87,146	86,689
Foreign
Schedule Of Geographical Information [Line Items]
Net service revenues									1,088,939	1,121,533	911,777
Assets, long-lived	$ 21,441				$ 20,826				$ 21,441	$ 20,826	$ 16,962