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Stockholders' Equity - Summary of Fair Value of Option Grant and ESPP Purchase Right on Grant Date Using Black-Scholes Option Pricing Model (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Payment Arrangement, Option      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Risk-free interest rate 0.50% 1.80% 2.80%
Dividend yield 0.00% 0.00% 0.00%
Volatility 69.40% 66.50% 70.40%
Expected life 6 years 6 years 6 years
Employee Stock Purchase Plan      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Risk-free interest rate 0.10% 1.90% 2.40%
Dividend yield 0.00% 0.00% 0.00%
Volatility 67.70% 52.10% 59.70%
Expected life 6 months 6 months 6 months