Comprehensive Income (Loss) (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Comprehensive (loss) income
Net income (loss)	$ (1,606)	$ (31,780)	$ 5,074	$ (56,350)
Unrealized gain on cash flow hedge, net of deferred taxes			7,784
Other	(6)	19	32	(25)
Comprehensive income (loss)	(712)	(30,046)	12,890	(51,094)
Interest rate swaps [Member]
Comprehensive (loss) income
Unrealized gain on cash flow hedge, net of deferred taxes	980	2,007	7,860	5,577
Comprehensive Income (Loss) (Textual) [Abstract]
Unrealized gain on cash flow hedge, deferred tax	548	1,092	4,366	3,121
Natural Gas Swaps [Member]
Comprehensive (loss) income
Unrealized gain on cash flow hedge, net of deferred taxes	(80)	(292)	(76)	(296)
Comprehensive Income (Loss) (Textual) [Abstract]
Unrealized gain on cash flow hedge, deferred tax	$ (45)	$ (165)	$ (43)	$ (165)