Summary of Provision for Income Taxes from Continuing Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current income taxes (benefit)
Federal	$ 2,045us-gaap_CurrentFederalTaxExpenseBenefit	$ 0us-gaap_CurrentFederalTaxExpenseBenefit	$ 0us-gaap_CurrentFederalTaxExpenseBenefit
State	1,504	0	(26)
Current income tax expense (benefit), total	3,549us-gaap_CurrentIncomeTaxExpenseBenefit	0us-gaap_CurrentIncomeTaxExpenseBenefit	(26)us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred income tax benefit
Federal	(130,693)	(77,046)	(60,676)
State	(4,534)	(650)	(8,000)
Deferred income tax benefit, total	(135,227)us-gaap_DeferredIncomeTaxExpenseBenefit	(77,696)us-gaap_DeferredIncomeTaxExpenseBenefit	(68,676)us-gaap_DeferredIncomeTaxExpenseBenefit
Income tax benefit	$ (131,678)us-gaap_IncomeTaxExpenseBenefit	$ (77,696)us-gaap_IncomeTaxExpenseBenefit	$ (68,702)us-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.