Quarterly Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, 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
Unaudited Quarterly Financial Data
Revenues	$ 269,399	$ 225,232	$ 236,775	$ 220,738	$ 213,329	$ 158,272	$ 183,879	$ 214,481	$ 952,144	$ 769,961	$ 872,845
Depreciation and amortization	34,594	32,367	29,271	29,057	27,285	25,254	25,951	27,071	125,289	105,561	116,567
Operating income	19,768	13,837	31,200	14,726	(27,630)	(32,616)	(20,693)	14,953	79,531	(65,986)	56,843
Income (loss) before income taxes and discontinued operations	7,706	(722)	13,432	(2,928)	(45,116)	(49,229)	(37,744)	(827)	17,488	(132,916)	16,857
(Provision) benefit for income taxes	(2,651)	(937)	(4,799)	967	12,593	17,403	11,697	(975)	(7,420)	40,718	(9,743)
Income (loss) from continuing operations	5,055	(1,659)	8,633	(1,961)	(32,523)	(31,826)	(26,047)	(1,802)	10,068	(92,198)	7,114
Income (loss) from discontinued operations, net of taxes	48	53	4	4	(255)	46	3,327	(48)	109	3,070	(7,137)
Net loss	$ 5,103	$ (1,606)	$ 8,637	$ (1,957)	$ (32,778)	$ (31,780)	$ (22,720)	$ (1,850)	$ 10,177	$ (89,128)	$ (23)
Net income (loss) per share	$ 0.11	$ (0.03)	$ 0.18	$ (0.04)	$ (0.69)	$ (0.67)	$ (0.48)	$ (0.04)	$ 0.21	$ (1.89)	$ 0.00
Net income (loss) per share, assuming dilution	$ 0.10	$ (0.03)	$ 0.17	$ (0.04)	$ (0.69)	$ (0.67)	$ (0.48)	$ (0.04)	$ 0.20	$ (1.89)	$ 0.00