Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Reconciliation of Warrant Liability Measured at Fair Value (Detail)

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Stockholders' Equity - Reconciliation of Warrant Liability Measured at Fair Value (Detail) - USD ($)
$ in Thousands
6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]    
Change in common stock warrant fair value $ 626 $ 974
Level 3 Inputs    
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]    
Beginning Balance 1,864  
Change in common stock warrant fair value 664  
Ending Balance 2,490  
Level 3 Inputs | Expired March 2016 Warrants    
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]    
Change in common stock warrant fair value $ (38)