Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Additional Information (Detail)

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Stockholders' Equity - Additional Information (Detail) - USD ($)
 12 Months Ended
Jul. 27, 2015
Jul. 25, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2013
Nov. 07, 2014
Sep. 30, 2013
Class of Stock [Line Items]              
Preferred stock, shares authorized     10,000,000 10,000,000      
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  
Net proceeds from public offering $ 21,100,000     $ 4,300,000      
Issued warrants to purchase common stock 8,200,000   23,447,003 23,447,003      
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     $ (75,000) $ (11,121,000)      
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]              
Issued warrants to purchase common stock     114,436        
Exercise price of common stock     $ 2.84        
Warrant term         10 years    
At the Market Facility [Member]              
Class of Stock [Line Items]              
Common stock shares sold       0