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Stock-Based Compensation - Schedule of Estimated Grant-date Fair Values of Stock-based Awards Using Black-Scholes Option Pricing Model Assumptions (Detail)
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected volatility, Minimum 83.00% 88.00% 83.00% 88.00%
Expected volatility, Maximum 85.00% 90.00% 85.00% 90.00%
Risk-free interest rate, Minimum 0.80% 0.40% 0.50% 0.40%
Risk-free interest rate, Maximum 1.10% 0.50% 1.10% 1.20%
Minimum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected term (in years) 5 years 3 months 19 days 5 years 3 months 19 days 5 years 3 months 19 days 5 years 3 months 19 days
Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected term (in years) 6 years 1 month 6 days 7 years 7 years 7 years