Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail)

v3.20.2
Stock-Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) - Employee Stock Options - $ / shares
3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Risk-free interest rate 0.49% 1.87% 1.47% 2.47%
Expected term (in years) 6 years 29 days 6 years 29 days 6 years 29 days 6 years 29 days
Dividend yield 0.00% 0.00% 0.00% 0.00%
Volatility 112.02% 107.21% 110.81% 108.67%
Weighted-average fair value of stock options granted $ 9.29 $ 4.96 $ 11.89 $ 4.36