Segment Information (Details 2) (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
Segment Information
Revenues	$ 85,980	$ 91,230	$ 92,784	$ 94,695	$ 100,051	$ 106,847	$ 106,635	$ 107,729	$ 364,689	$ 421,262	$ 452,172
Property and equipment	105,516				119,164				105,516	119,164	156,917
United States
Segment Information
Revenues									342,685	394,601	423,883
Property and equipment	95,709				108,680				95,709	108,680	142,713
Canada
Segment Information
Revenues									19,339	23,448	24,804
Property and equipment	5,614				6,645				5,614	6,645	9,826
Mexico
Segment Information
Revenues									1,802	2,255	2,414
Property and equipment	4,193				3,839				4,193	3,839	4,378
Other
Segment Information
Revenues									$ 863	$ 958	$ 1,071