Income Taxes (Income Tax Provision (Benefit)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current income tax expense (benefit)
Federal	$ (42,500)us-gaap_CurrentFederalTaxExpenseBenefit	$ 393us-gaap_CurrentFederalTaxExpenseBenefit	$ 57,720us-gaap_CurrentFederalTaxExpenseBenefit
State	(407)	9,864	18,034
Total current income tax expense (benefit)	(42,907)us-gaap_CurrentIncomeTaxExpenseBenefit	10,257us-gaap_CurrentIncomeTaxExpenseBenefit	75,754us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred income tax expense (benefit)
Federal	400,544	222,559	239,862
State	29,429	(33)	15,881
Total deferred income tax expense	429,973us-gaap_DeferredIncomeTaxExpenseBenefit	222,526us-gaap_DeferredIncomeTaxExpenseBenefit	255,743us-gaap_DeferredIncomeTaxExpenseBenefit
Total income tax expense	$ 387,066us-gaap_IncomeTaxExpenseBenefit	$ 232,783us-gaap_IncomeTaxExpenseBenefit	$ 331,497us-gaap_IncomeTaxExpenseBenefit

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.