Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Summary of Fair Values of Stock Options Granted and Assumptions used in Black-Scholes Model (Detail)

v3.20.2
Stock-Based Compensation - Summary of Fair Values of Stock Options Granted and Assumptions used in Black-Scholes Model (Detail) - Stock Options [Member] - $ / shares
9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Estimated fair values of stock options granted $ 3.32 $ 10.70
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 0.30% 1.90%
Expected volatility 77.40% 77.90%
Expected term (in years) 6 years 6 years 9 months 18 days
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 1.70% 2.50%
Expected volatility 81.20% 78.90%
Expected term (in years) 10 years 10 years