Annual report pursuant to Section 13 and 15(d)

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

v3.7.0.1
Stockholders' Equity - Reconciliation of Warrant Liability Measured at Fair Value (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]      
Change in common stock warrant value $ (121) $ (16,773) $ (9,344)
Level 3 Inputs      
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]      
Beginning Balance 1,864 3,961 23,421
Initial fair value of common stock warrant related to February 2015 offering   14,693  
Exercise of warrants   (17) (10,116)
Change in common stock warrant value (83) (16,773) (9,344)
Ending Balance 1,743 $ 1,864 $ 3,961
Level 3 Inputs | Expired March 2016 Warrants      
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]      
Change in common stock warrant value $ (38)