Income Taxes - Provision for Income Tax (Benefit) Expense (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
Federal	$ 69,245us-gaap_CurrentFederalTaxExpenseBenefit	$ 349us-gaap_CurrentFederalTaxExpenseBenefit	$ 34us-gaap_CurrentFederalTaxExpenseBenefit
State	135	169	118
Total	69,380us-gaap_CurrentIncomeTaxExpenseBenefit	518us-gaap_CurrentIncomeTaxExpenseBenefit	152us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred:
Federal	35,314	(366)	196
State	10,813	(561)	39
Total	46,127us-gaap_DeferredIncomeTaxExpenseBenefit	(927)us-gaap_DeferredIncomeTaxExpenseBenefit	235us-gaap_DeferredIncomeTaxExpenseBenefit
Income tax expense (benefit)	$ 115,507us-gaap_IncomeTaxExpenseBenefit	$ (409)us-gaap_IncomeTaxExpenseBenefit	$ 387us-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.