Segment Information Segment Information (Schedule of Revenue by Geographic Area) (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	$ 139,955	$ 157,869	$ 133,212	$ 139,253	$ 143,299	$ 151,911	$ 117,540	$ 112,384	$ 570,289	$ 525,134	$ 497,421
United States
Revenues									558,138	516,466	490,409
Canada
Revenues									9,645	5,180	4,646
Mexico
Revenues									$ 2,506	$ 3,488	$ 2,366