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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
Mar. 31, 2021
Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility, Minimum 84.00% 88.00%
Expected volatility, Maximum 85.00% 90.00%
Risk-free interest rate, Minimum 0.50% 0.60%
Risk-free interest rate, Maximum 1.10% 1.20%
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term (in years) 5 years 6 months 5 years 8 months 12 days
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term (in years) 7 years 6 years 8 months 12 days