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Stock-Based Compensation - Schedule of Fair Value of Employee Stock Options (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Employee | Options to purchase common stock    
Share-based Compensation    
Expected volatility, Minimum 74.40% 65.10%
Expected volatility, Maximum 79.30% 74.40%
Risk-free interest rate, Minimum 0.22% 1.46%
Risk-free interest rate, Maximum 1.63% 2.52%
Minimum | Employee | Options to purchase common stock    
Share-based Compensation    
Expected term (in years) 6 years 25 days 5 years 3 months 18 days
Maximum | Employee | Options to purchase common stock    
Share-based Compensation    
Expected term (in years) 6 years 29 days 6 years 1 month 6 days
2016 Employee Stock Purchase Plan    
Share-based Compensation    
Expected volatility, Minimum 44.70% 39.60%
Expected volatility, Maximum 100.70% 74.20%
Risk-free interest rate, Minimum 0.12% 1.67%
Risk-free interest rate, Maximum 1.68% 2.66%
2016 Employee Stock Purchase Plan | Minimum    
Share-based Compensation    
Expected term (in years) 6 months 6 months
2016 Employee Stock Purchase Plan | Maximum    
Share-based Compensation    
Expected term (in years) 1 year 1 year