Income Taxes - Provision (Benefit) for Income Tax Attributable to Income (Loss) from Continuing Operations before Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
Federal	$ (109,565)us-gaap_CurrentFederalTaxExpenseBenefit	$ 21,773us-gaap_CurrentFederalTaxExpenseBenefit	$ 1,457us-gaap_CurrentFederalTaxExpenseBenefit
State	5,339	1,646	122
Total current taxes	(104,226)us-gaap_CurrentIncomeTaxExpenseBenefit	23,419us-gaap_CurrentIncomeTaxExpenseBenefit	1,579us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred:
Federal	147,797	(107,651)	33,446
State	196	(1,929)	3,885
Total deferred taxes	147,993us-gaap_DeferredIncomeTaxExpenseBenefit	(109,580)us-gaap_DeferredIncomeTaxExpenseBenefit	37,331us-gaap_DeferredIncomeTaxExpenseBenefit
Total income tax expense (benefit)	$ 43,767us-gaap_IncomeTaxExpenseBenefit	$ (86,161)us-gaap_IncomeTaxExpenseBenefit	$ 38,910us-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.