Quarterly report pursuant to Section 13 or 15(d)

Common Stock Warrants - Additional Information (Detail)

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Common Stock Warrants - Additional Information (Detail) - USD ($)
 1 Months Ended 3 Months Ended 9 Months Ended
Aug. 31, 2015
Jan. 31, 2014
Sep. 30, 2015
Sep. 30, 2015
Sep. 30, 2014
Class of Warrant or Right [Line Items]          
Issuance of common stock upon exercise of warrants     0 132,295  
Issuance of common stock upon exercise of warrants on cash basis       74,136  
Proceeds from issuance of common stock upon warrant exercises       $ 426,000  
Issuance of common stock in accordance with net exercise provisions       58,159  
Fair value reclassification of warrant liability to additional paid-in capital     $ 0 $ 1,500,000  
Issued warrants to purchase common stock 114,436   114,436 114,436  
Proceeds from sale of common stock       $ 25,375,000 $ 25,430,000
Exercise price of common stock $ 2.84   $ 2.84 $ 2.84  
Warrant term 10 years     10 years  
Fair value of warrant liabilities $ 300,000 $ 400,000 $ 300,000 $ 300,000  
Warrants, Exercise price of $5.75 per share [Member]          
Class of Warrant or Right [Line Items]          
Issued warrants to purchase common stock   120,800      
Proceeds from sale of common stock   $ 3,000,000      
Exercise price of common stock   $ 5.75      
Warrant term   5 years