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 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total Stock based compensation $ 37,804 $ 274,140 $ 243,565 $ 386,280
Research and Development [Member]        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total Stock based compensation (129,684) 82,953 (96,051) 103,870
Selling, General and Administrative [Member]        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Total Stock based compensation $ 167,488 $ 191,187 $ 339,616 $ 282,410