Income Taxes (Components of Income Tax Expense (Benefit)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CurrentIncomeTaxExpenseBenefitContinuingOperationsAbstract
CurrentFederalTaxExpenseBenefit	$ (8,499)us-gaap_CurrentFederalTaxExpenseBenefit	$ 36,759us-gaap_CurrentFederalTaxExpenseBenefit	$ 26,637us-gaap_CurrentFederalTaxExpenseBenefit
CurrentStateAndLocalTaxExpenseBenefit	0	0	0
Current Income Tax Expense (Benefit)	(8,499)us-gaap_CurrentIncomeTaxExpenseBenefit	36,759us-gaap_CurrentIncomeTaxExpenseBenefit	26,637us-gaap_CurrentIncomeTaxExpenseBenefit
DeferredIncomeTaxExpenseBenefitContinuingOperationsAbstract
DeferredFederalIncomeTaxExpenseBenefit	17,103	295,613	196,997
DeferredStateAndLocalIncomeTaxExpenseBenefit	0	0	0
Deferred Income Tax Expense (Benefit)	17,103us-gaap_DeferredIncomeTaxExpenseBenefit	295,613us-gaap_DeferredIncomeTaxExpenseBenefit	196,997us-gaap_DeferredIncomeTaxExpenseBenefit
Total income tax expense (benefit) on continuing operations	8,604us-gaap_IncomeTaxExpenseBenefit	332,372us-gaap_IncomeTaxExpenseBenefit	223,634us-gaap_IncomeTaxExpenseBenefit
IncomeTaxEffectsAllocatedDirectlyToEquityAbstract
Other comprehensive income (loss)	7,407us-gaap_OtherComprehensiveIncomeLossTax	(41,149)us-gaap_OtherComprehensiveIncomeLossTax	(7,218)us-gaap_OtherComprehensiveIncomeLossTax
AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation	0	4,354	5,730
Total income taxes	$ 16,011	$ 295,577	$ 222,146

Amount of increase in additional paid in capital (APIC) resulting from a tax benefit associated with share-based compensation plan other than an employee stock ownership plan (ESOP). Includes, but is not limited to, excess tax benefit.

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

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

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

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

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

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

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The sum of income tax expense or benefit for the period that has been allocated among continuing operations, discontinued operations, extraordinary items, other comprehensive income, and items charged or credited directly to shareholders' equity.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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