Business Segment Information (Schedule of Revenues And Assets Based On Location) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues	$ 299,024	$ 280,655	$ 274,574	$ 271,879	$ 261,635	$ 251,752	$ 241,237	$ 237,898	$ 1,126,132	$ 992,522	$ 929,727
Assets	1,439,169				1,309,824				1,439,169	1,309,824
United States [Member]
Revenues									962,266	843,407	785,506
Assets	1,231,565				1,066,451				1,231,565	1,066,451
International Operations [Member]
Revenues									163,866	149,115	144,221
Assets	$ 207,604				$ 243,373				$ 207,604	$ 243,373