Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Additional Information (Detail)

v3.20.1
Stockholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 12 Months Ended
Dec. 12, 2019
Sep. 14, 2018
Mar. 08, 2018
Sep. 30, 2016
Jun. 21, 2016
Apr. 30, 2019
Dec. 31, 2019
Dec. 31, 2018
Jun. 18, 2019
Jun. 17, 2019
May 07, 2014
Schedule Of Capitalization Equity [Line Items]                      
Common stock, par value (in dollars per share)             $ 0.001 $ 0.001      
Common stock, shares authorized (in shares)             250,000,000 125,000,000 250,000,000 125,000,000  
Common stock, shares issued (in shares)             97,413,721 47,971,989      
Common stock, shares outstanding (in shares)             97,413,721 47,971,989      
Preferred stock, shares authorized (in shares)             5,000,000 5,000,000     5,000,000
Preferred stock, par value (in dollars per share)             $ 0.001 $ 0.001     $ 0.001
Preferred stock, shares issued (in shares)             0 0      
Preferred stock, shares outstanding (in shares)             0 0      
Derivative liability fair value adjustment             $ 1,567 $ 0      
Common stock issued, net of expenses (in shares)     17,751,500   9,375,000            
Number of warrants issued to purchase common stock (in shares)   13,198,075                  
Warrants, expiration date   Mar. 14, 2019                  
Warrant liabilities fair value adjustment             4,497 $ (11,866)      
Warrant liabilities             18,400        
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              
June 2016 Public Offering                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares)   4,218,750                  
Exercise price of warrants (in dollars per share)   $ 3.00     $ 3.00            
Number of shares received per warrant (in shares)         0.45            
Warrant expiration period         5 years            
March 2018 Public Offering                      
Schedule Of Capitalization Equity [Line Items]                      
Common stock issued, net of expenses (in shares)     17,751,500                
Number of warrants issued to purchase common stock (in shares)     21,301,800                
December 2019 Public Offering                      
Schedule Of Capitalization Equity [Line Items]                      
Common stock issued, net of expenses (in shares) 38,888,889                    
Number of warrants issued to purchase common stock (in shares) 38,888,889                    
Exercise price of warrants (in dollars per share) $ 1.10                    
Warrants, expiration date Jun. 12, 2023                    
Warrant liabilities fair value adjustment             1,000        
Underwriters | Maximum                      
Schedule Of Capitalization Equity [Line Items]                      
Option to purchase shares of common stock 5,833,333                    
Warrant liability | June 2016 Public Offering | Maximum                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares)         4,218,750            
Warrant liability | March 2018 Public Offering | Maximum                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares)     21,301,800                
Warrant liability | December 2019 Public Offering | Maximum                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares) 38,888,889                    
Warrant liability | Underwriters                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares) 5,833,333                    
Number of warrants exercised 5,833,333                    
Series 1 Warrant                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares)               115,550      
Proceeds from Warrant Exercises               $ 200      
Warrants, expiration date     Mar. 14, 2019                
Series 1 Warrant | March 2018 Public Offering                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares)   13,198,075                  
Exercise price of warrants (in dollars per share)   $ 1.85 $ 1.85                
Number of shares received per warrant (in shares)     0.75                
Warrant term     371 days                
Series 1 Warrant | March 2018 Public Offering | Maximum                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares)     13,313,625                
Series 2 Warrant | March 2018 Public Offering                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares)   7,988,175                  
Exercise price of warrants (in dollars per share)   $ 2.00 $ 2.00                
Number of shares received per warrant (in shares)     0.45                
Warrant term     5 years                
Series 2 Warrant | March 2018 Public Offering | Maximum                      
Schedule Of Capitalization Equity [Line Items]                      
Number of warrants issued to purchase common stock (in shares)     7,988,175                
Senior Convertible Note Purchase Agreement                      
Schedule Of Capitalization Equity [Line Items]                      
Conversion of convertible note, amount           $ 2,000          
Conversion of convertible note exchanged for shares           1,626,000          
Senior Convertible Note Purchase Agreement | Other (Income) Expense                      
Schedule Of Capitalization Equity [Line Items]                      
Derivative liability fair value adjustment             $ 1,600