v3.20.1
Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Shares, Outstanding at beginning balance 3,351,132 1,912,980  
Shares, Granted 4,666,728 1,615,200  
Shares, Exercised 0 (52,099)  
Shares, Expired/cancelled (2,682,010) (124,949)  
Shares, Outstanding at ending balance 5,335,850 3,351,132 1,912,980
Shares, Expected to vest 2,395,265 2,197,619  
Shares, Options exercisable 2,940,585 1,153,513  
Weighted Average Exercise Price, Outstanding at beginning balance $ 3.73 $ 3.72  
Weighted Average Exercise Price, Granted 1.85 3.64  
Weighted Average Exercise Price, Exercised   1.47  
Weighted Average Exercise Price, Expired/cancelled 2.70 3.23  
Weighted Average Exercise Price, Outstanding at ending balance 2.60 3.73 $ 3.72
Weighted Average Exercise Price, Expected to vest 1.93 4.17  
Weighted Average Exercise Price, Options exercisable $ 3.15 $ 2.90  
Weighted Average Remaining Contractual Term, Outstanding 6 years 2 months 23 days 8 years 2 months 26 days 8 years 2 months 26 days
Weighted Average Remaining Contractual Term, Expected to vest 9 years 9 years 2 months 8 days  
Weighted Average Remaining Contractual Term, Options exercisable 3 years 11 months 23 days 6 years 4 months 13 days  
Aggregate Intrinsic Value, Outstanding $ 2,866 $ 142,788 $ 2,738,704
Aggregate Intrinsic Value, Expected to vest $ 2,866    
Aggregate Intrinsic Value, Options exercisable   $ 142,788