Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Current portion of income tax expense:
Federal	$ 0	$ 2,212	$ 0	$ 9,156
State	132	224	261	399
Deferred portion of income tax expense	(14,927)	(70,415)	(30,215)	(52,241)
Total Income tax expense	(14,795)	(72,851)	(30,476)	(61,796)
Effective tax rate (as a percent)	37.30%	36.90%	37.30%	36.80%
Amount of refund received from net operating loss carryback claim		$ 5,500