Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

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Stockholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, shares in Millions
3 Months Ended 6 Months Ended
Mar. 16, 2016
Jun. 30, 2016
Jun. 30, 2016
Dec. 31, 2015
February 2015 Warrants        
Class Of Warrant Or Right [Line Items]        
Warrants to purchase shares of common stock   8.3 8.3 8.3
Warrant exercise price   $ 3.62 $ 3.62 $ 10.86
February 2015 Warrants | Warrants        
Class Of Warrant Or Right [Line Items]        
Change in fair value of common stock warrants   $ 1,000,000 $ 700,000  
March 2011 Warrants        
Class Of Warrant Or Right [Line Items]        
Warrants to purchase shares of common stock       3.8
Warrant exercise price       $ 2.46
Number of outstanding warrants that expired 3.8      
March 2011 Warrants | Warrants        
Class Of Warrant Or Right [Line Items]        
Change in fair value of common stock warrants $ 38,000