Comprehensive Income (Details) (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
Comprehensive Income
Net income (loss)	$ 10,696	$ 8,863	$ (109,705)	$ 6,793	$ 14,728	$ 12,128	$ 9,425	$ 7,917	$ (83,353)	$ 44,198	$ 53,604
Other comprehensive income:
Adjustment to pension liability									(9,544)	(17,173)	(2,627)
Tax benefit									3,818	6,869	1,051
Adjustment to pension liability, net of tax									(5,726)	(10,304)	(1,576)
Foreign currency translation adjustments									1,315	(1,337)	(136)
Total other comprehensive loss, net of tax									(4,411)	(11,641)	(1,712)
Comprehensive income (loss)									$ (87,764)	$ 32,557	$ 51,892