Geographic Information (Revenues By Geographic Areas) (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	$ 813,760	$ 858,424	$ 847,596	$ 806,326	$ 757,235	$ 802,577	$ 804,890	$ 768,875	$ 3,326,106	$ 3,133,577	$ 2,766,859
United States [Member]
Revenues									2,951,673	2,798,124	2,474,805
Canada [Member]
Revenues									227,756	218,570	198,592
Other Foreign Countries [Member]
Revenues									$ 146,677	$ 116,883	$ 93,462