Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Additional Information (Detail)

v3.19.1
Stockholders' Equity - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Mar. 08, 2018
Sep. 30, 2016
Jun. 21, 2016
Jul. 31, 2006
Dec. 31, 2018
Dec. 31, 2017
Sep. 14, 2018
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)         125,000,000 125,000,000    
Common stock, shares issued (in shares)         47,971,989 28,971,651    
Common stock, shares outstanding (in shares)         47,971,989 28,971,651    
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    
Common stock issued, net of expenses (in shares) 17,751,500   9,375,000          
Warrant liabilities fair value adjustment         $ (11,866,000) $ (2,729,000)    
Warrant liabilities         $ 1,000,000      
Warrants to purchase common stock associated with Solar 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]                
Number of warrants issued to purchase common stock (in shares) 21,301,800              
Common stock issued, net of expenses (in shares) 17,751,500              
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              
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         $ 200,000      
warrants expiration 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              
Series C-1 Convertible Preferred Stock [Member]                
Schedule Of Capitalization Equity [Line Items]                
Number of warrants issued to purchase common stock (in shares)       196,923        
Exercise price of warrants (in dollars per share)       $ 3.25        
Fair value of warrants       $ 500,000        
Derivative Liability         $ 0 $ 0    
Common Stock                
Schedule Of Capitalization Equity [Line Items]                
Number of warrants issued to purchase common stock (in shares)       14,033        
Exercise price of warrants (in dollars per share)       $ 45.61