Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation - Fair Value of Employee Stock Options Granted and ESPP Rights to Purchase Common Stock Calculated Using Black Scholes Option Pricing Model with Weighted Average Assumptions (Details)

v3.20.4
Stock-Based Compensation - Fair Value of Employee Stock Options Granted and ESPP Rights to Purchase Common Stock Calculated Using Black Scholes Option Pricing Model with Weighted Average Assumptions (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected dividend yield 0.00%    
Employee options      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected volatility, Minimum 83.80% 78.70% 82.00%
Expected volatility, Maximum 91.90% 83.70% 83.20%
Risk-free interest rate, Minimum 0.40% 1.50% 2.60%
Risk-free interest rate, Maximum 1.60% 2.60% 3.10%
ESPP Rights      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected term (years) 6 months 6 months 6 months
Expected volatility     74.30%
Expected volatility, Minimum 101.70% 73.70%  
Expected volatility, Maximum 114.30% 109.90%  
Risk-free interest rate     2.50%
Risk-free interest rate, Minimum 0.10% 1.60%  
Risk-free interest rate, Maximum 0.20% 2.40%  
Minimum | Employee options      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected term (years) 5 years 6 months 5 years 9 months 18 days 5 years 6 months
Maximum | Employee options      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected term (years) 6 years 5 years 10 months 24 days 6 years 1 month 6 days