Quarterly Financial Information (Details) (USD $) In Thousands, except Per Share data, 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
Revenues	$ 301,600		$ 304,200		$ 298,300		$ 293,000		$ 275,800		$ 295,900		$ 289,400		$ 280,100		$ 1,197,103	$ 1,141,198	$ 1,058,568
Operating income (loss)	11,900		33,000		38,800		43,500		37,100		37,500		22,000		32,100		127,221	128,610	52,185
Income (loss) from continuing operations	(42,000)		6,800		12,900		(300)		17,700		11,800		(5,200)		5,900		(22,639)	30,196	(40,841)
Income (loss) from discontinued operations, net of income taxes	(400)		(7,100)		(1,000)		(700)		7,300		(12,600)		(23,900)		(3,600)		(9,166)	(32,735)	17,422
Net loss	$ (42,400)		$ (300)		$ 12,000		$ (1,000)		$ 25,000		$ (800)		$ (29,100)		$ 2,400		$ (31,805)	$ (2,539)	$ (23,419)
Income (loss) from continuing operations	$ (0.71)	[1]	$ 0.11	[1]	$ 0.21	[1]	$ (0.01)	[1]	$ 0.28	[1]	$ 0.19	[1]	$ (0.08)	[1]	$ 0.10	[1]	$ (0.37)	$ 0.49	$ (0.67)
Income (loss) from discontinued operations, net of income taxes	$ (0.01)	[1]	$ (0.12)	[1]	$ (0.02)	[1]	$ (0.01)	[1]	$ 0.12	[1]	$ (0.20)	[1]	$ (0.39)	[1]	$ (0.06)	[1]	$ (0.15)	$ (0.53)	$ 0.29
Net income (loss)- basic	$ (0.72)	[1]	$ (0.01)	[1]	$ 0.19	[1]	$ (0.02)	[1]	$ 0.40	[1]	$ (0.01)	[1]	$ (0.47)	[1]	$ 0.04	[1]	$ (0.52)	$ (0.04)	$ (0.38)
Income (loss) from continuing operations	$ (0.71)	[1]	$ 0.10	[1]	$ 0.21	[1]	$ (0.01)	[1]	$ 0.28	[1]	$ 0.19	[1]	$ (0.08)	[1]	$ 0.10	[1]	$ (0.37)	$ 0.48	$ (0.67)
Income (loss) from discontinued operations, net of income taxes	$ (0.01)	[1]	$ (0.11)	[1]	$ (0.02)	[1]	$ (0.01)	[1]	$ 0.12	[1]	$ (0.20)	[1]	$ (0.39)	[1]	$ (0.06)	[1]	$ (0.15)	$ (0.52)	$ 0.29
Net income (loss)- diluted	$ (0.72)	[1]	$ (0.01)	[1]	$ 0.19	[1]	$ (0.02)	[1]	$ 0.40	[1]	$ (0.01)	[1]	$ (0.47)	[1]	$ 0.04	[1]	$ (0.52)	$ (0.04)	$ (0.38)

[1] Net income (loss) per share calculations for each quarter is based on the weighted average number of shares outstanding during the respective periods; accordingly, the sum of the quarters may not equal the full-year income (loss) per share.