Summary of Significant Accounting Policies - Reconciliation of Liabilities Measured at Fair Value Using Significant Observable Inputs Level 3 (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 53,000
Changes in fair value	(1,000)
Ending Balance	52,000
Warrants and Rights Outstanding [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	5,093
Changes in fair value	(410)
Ending Balance	$ 4,683