Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies - Additional Information (Detail)

v3.10.0.1
Significant Accounting Policies - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Apr. 10, 2015
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Summary Of Significant Accounting Policies [Line Items]          
Research and development expense, total   $ 7,639,974 $ 8,692,003 $ 16,361,526 $ 17,045,187
Liability for unrecognized tax benefits   0   $ 0  
Interest or penalties for uncertian tax positions   $ 0 $ 0    
Antidilutive securities excluded from computation of earnings per share, amount   7,403,916 7,532,800 7,403,916 7,532,800
Employee Stock Purchase Plan [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Common stock purchase price discount percentage 85.00%     15.00%