Quarterly report pursuant to Section 13 or 15(d)

Stock-based Compensation - Stock-based Compensation Expense Recognized (Detail)

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Stock-based Compensation - Stock-based Compensation Expense Recognized (Detail) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total Stock based compensation $ 34,109 $ 1,538,343 $ 290,830 $ 1,624,165
Research and Development Expense [Member]
       
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total Stock based compensation 18,217 183,168 155,984 158,575
Selling, General and Administrative Expenses [Member]
       
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total Stock based compensation $ 15,892 $ 1,355,175 $ 134,846 $ 1,465,590