Benefit for Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Income Taxes [Line Items]
Current		$ 34us-gaap_CurrentFederalTaxExpenseBenefit	$ 52us-gaap_CurrentFederalTaxExpenseBenefit
Deferred	(40,209)	(2,695)	(10,572)
Total U.S.	(40,209)	(2,661)	(10,520)
Current	0us-gaap_CurrentForeignTaxExpenseBenefit	0us-gaap_CurrentForeignTaxExpenseBenefit	0us-gaap_CurrentForeignTaxExpenseBenefit
Deferred		(34)	(52)
Total Foreign		(34)	(52)
Benefit from income taxes	$ (40,209)us-gaap_IncomeTaxExpenseBenefit	$ (2,695)us-gaap_IncomeTaxExpenseBenefit	$ (10,572)us-gaap_IncomeTaxExpenseBenefit

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