Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)

v3.6.0.2
Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Assets    
Total assets $ 25,735 $ 55,458
Warrant [Member]    
Liabilities    
Liabilities 232 1,105
Cash [Member]    
Assets    
Total assets 1,800 14,034
Money market securities (cash equivalents) [Member]    
Assets    
Total assets 11,931 20,276
Corporate bonds and commercial paper (cash equivalents) [Member]    
Assets    
Total assets 1,502  
Government securities [Member]    
Assets    
Total assets 2,000  
Restricted cash [Member]    
Assets    
Total assets 272 272
Corporate bonds and commercial paper (short term investments) [Member]    
Assets    
Total assets 8,230 20,876
Level 1 [Member]    
Assets    
Total assets 17,505 34,582
Level 1 [Member] | Cash [Member]    
Assets    
Total assets 1,800 14,034
Level 1 [Member] | Money market securities (cash equivalents) [Member]    
Assets    
Total assets 11,931 20,276
Level 1 [Member] | Corporate bonds and commercial paper (cash equivalents) [Member]    
Assets    
Total assets 1,502  
Level 1 [Member] | Government securities [Member]    
Assets    
Total assets 2,000  
Level 1 [Member] | Restricted cash [Member]    
Assets    
Total assets 272 272
Level 2 [Member]    
Assets    
Total assets 8,230 20,876
Level 2 [Member] | Corporate bonds and commercial paper (short term investments) [Member]    
Assets    
Total assets 8,230 20,876
Level 3 [Member] | Warrant [Member]    
Liabilities    
Liabilities $ 232 $ 1,105