Business Segments (Revenues And Long-Lived Assets By Geographic Location) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues from External Customers and Long-Lived Assets [Line Items]
Net service revenues	$ 973,473	$ 984,668	$ 937,966	$ 880,869	$ 851,572	$ 817,258	$ 769,090	$ 737,173	$ 3,776,976	$ 3,175,093	$ 3,036,547
Assets, long-lived	107,972				103,651				107,972	103,651	124,658
Domestic [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net service revenues									2,655,443	2,263,316	2,161,826
Assets, long-lived	87,146				86,689				87,146	86,689	101,034
Foreign [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net service revenues									1,121,533	911,777	874,721
Assets, long-lived	$ 20,826				$ 16,962				$ 20,826	$ 16,962	$ 23,624