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 9 Months Ended
Apr. 10, 2015
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Summary Of Significant Accounting Policies [Line Items]          
Research and development expense, total   $ 8,442,698 $ 8,743,434 $ 24,804,224 $ 25,788,621
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   6,840,737 7,862,420 6,840,737 7,862,420
Employee Stock Purchase Plan [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Common stock purchase price discount percentage 85.00%     15.00%