Quarterly report pursuant to Section 13 or 15(d)

Stockholder's Equity - Additional Information (Detail)

v3.19.1
Stockholder's Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended
Sep. 30, 2016
Apr. 30, 2019
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Sep. 14, 2018
Schedule Of Capitalization Equity [Line Items]            
Common stock, par value (in dollars per share)     $ 0.001   $ 0.001  
Common stock, shares authorized (in shares)     125,000,000   125,000,000  
Common stock, shares issued (in shares)     50,232,429   47,971,989  
Common stock, shares outstanding (in shares)     50,232,429   47,971,989  
Warrant liabilities fair value adjustment     $ 6,522 $ (3,554)    
Warrant liabilities     $ 7,500      
Number of warrants issued to purchase common stock (in shares)           13,198,075
Warrants to purchase common stock associated with Loan Agreement            
Schedule Of Capitalization Equity [Line Items]            
Number of warrants issued to purchase common stock (in shares) 122,435          
Exercise price of warrants (in dollars per share) $ 3.6754          
Warrant expiration period 5 years          
Senior Convertible Note Purchase Agreement | Subsequent Event            
Schedule Of Capitalization Equity [Line Items]            
Conversion of convertible note, amount   $ 2,000        
Conversion of convertible note exchanged for shares   1,626,000