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Summary of Significant Accounting Policies - Additional Information (Detail)
 1 Months Ended 12 Months Ended
Jun. 21, 2016
$ / shares
shares
Apr. 28, 2015
$ / shares
shares
May 07, 2014
$ / shares
shares
Apr. 30, 2015
Aug. 31, 2013
USD ($)
Dec. 31, 2016
USD ($)
segment
shares
Dec. 31, 2015
USD ($)
shares
Dec. 31, 2014
USD ($)
Accounting Policies [Abstract]                
Shelf registration (years)       3 years        
Deferred offering costs | $           $ 345,000 $ 417,000  
Subsidiary, Sale of Stock [Line Items]                
Number of shares of common stock sold (in shares) | shares   5,376,622 6,200,000     10,696,456 5,376,622  
Number of warrants issued to purchase common stock (in shares) | shares           14,033 14,033  
Public offering price (in dollars per share) | $ / shares   $ 7.70 $ 10.00          
Upfront payment received | $         $ 1,500,000      
Deferred revenue recognition period (in months)         70 months      
Revenue recognized from upfront payments | $           $ 257,000 $ 257,000 $ 256,000
Revenue from asset purchase agreement | $           $ 0    
Operating segments (number) | segment           1    
June 2016 Public Offering                
Subsidiary, Sale of Stock [Line Items]                
Number of shares of common stock sold (in shares) | shares 9,375,000              
Number of warrants issued to purchase common stock (in shares) | shares 4,218,750              
Public offering price (in dollars per share) | $ / shares $ 2.40