Income Taxes (Details 2) (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
Current:
Federal									$ (3,493)	$ (310)	$ (108,827)
State									8,395	15,140	25,545
Total current									4,902	14,830	(83,282)
Deferred:
Federal									200,322	159,566	260,236
State									28,280	16,626	10,911
Discontinued operations											(10,736)
Total deferred									228,602	176,192	260,411
Total income tax expense									233,504	191,022	177,129
Less: income tax expense (benefit) on discontinued operations									(3,813)	7,418	16,260
Income tax expense - continuing operations	$ 18,157	$ 147,116	$ 76,689	$ (4,645)	$ 7,375	$ 131,416	$ 50,818	$ (6,005)	$ 237,317	$ 183,604	$ 160,869