Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies - Additional Information (Detail)

v3.19.2
Significant Accounting Policies - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Apr. 30, 2015
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Summary Of Significant Accounting Policies [Line Items]          
Research and development expense, total   $ 5,515,017 $ 7,639,974 $ 12,315,695 $ 16,361,526
Liability for unrecognized tax benefits   0   0  
Interest or penalties for uncertain tax positions   $ 0 $ 0 $ 0 $ 0
Antidilutive securities excluded from computation of earnings per share, amount   7,228,185 7,403,916 7,228,185 7,403,916
Employee Stock Purchase Plan [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Common stock purchase price discount percentage 85.00%     15.00%