Income Taxes--Component of Income Tax Expense (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current tax expense
Federal tax benefit	$ (22)us-gaap_CurrentFederalTaxExpenseBenefit	$ (29)us-gaap_CurrentFederalTaxExpenseBenefit	$ (23)us-gaap_CurrentFederalTaxExpenseBenefit
State tax expense	574	1,144	141
Current tax expense	552us-gaap_CurrentIncomeTaxExpenseBenefit	1,115us-gaap_CurrentIncomeTaxExpenseBenefit	118us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred tax expense
Federal tax expense	115,699	30,327	35,579
State tax expense	8,192	1,407	2,140
Deferred tax expense	123,891us-gaap_DeferredIncomeTaxExpenseBenefit	31,734us-gaap_DeferredIncomeTaxExpenseBenefit	37,719us-gaap_DeferredIncomeTaxExpenseBenefit
Income tax expense	$ 124,443us-gaap_IncomeTaxExpenseBenefit	$ 32,849us-gaap_IncomeTaxExpenseBenefit	$ 37,837us-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.