Annual report pursuant to Section 13 and 15(d)

Common Stock - Additional Information (Detail)

v3.3.1.900
Common Stock - Additional Information (Detail) - USD ($)
 12 Months Ended
Jul. 27, 2015
Jul. 25, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Aug. 31, 2015
Nov. 07, 2014
Sep. 30, 2013
Class of Stock [Line Items]                
Common stock, shares authorized     100,000,000 100,000,000        
Common stock shares sold   4,600,000            
Common stock offering price $ 2.81 $ 5.50            
Net proceeds from public offering   $ 23,000,000            
Registration filed on Form S-3             $ 100,000,000  
Registration statement, event description     Entered into an at-the-market facility (ATM) to sell up to $25 million of common stock under the registration statement.          
Registration statement, sale of common stock             $ 25,000,000  
Proceeds from sale of common stock $ 21,100,000   $ 4,300,000          
Common stock, shares issued 8,188,000   23,447,003 14,696,108        
Issued warrants to purchase common stock     114,436          
Exercise price of common stock     $ 2.84          
Warrant term     10 years          
Change in fair value of warrant liability     $ (11,121,000) $ 7,236,000        
Warrants, Exercise price of $5.75 per share [Member]                
Class of Stock [Line Items]                
Issued warrants to purchase common stock         1,741,788      
Exercise price of common stock         $ 5.75      
Warrant term         5 years      
Warrants, Exercise Price of $5.00 Per Share [Member]                
Class of Stock [Line Items]                
Issued warrants to purchase common stock               121,739
Exercise price of common stock               $ 5.00
Warrant term         7 years      
Warrants, Exercise Price of $2.84 Per Share [Member]                
Class of Stock [Line Items]                
Common stock, shares issued           114,436    
Exercise price of common stock           $ 2.84    
At the Market Facility [Member]                
Class of Stock [Line Items]                
Common stock shares sold     0