Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies - Additional Information (Detail)

v3.19.3
Significant Accounting Policies - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Apr. 30, 2015
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Summary Of Significant Accounting Policies [Line Items]          
Research and development expense, total   $ 5,190,056 $ 8,442,698 $ 17,505,751 $ 24,804,224
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   6,876,595 6,840,737 6,876,595 6,840,737
Employee Stock Purchase Plan [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Common stock purchase price discount percentage 85.00%     15.00%