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Equity Incentive Plans - Summary of Estimated Fair Value of Options Granted (Details) - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Grant date fair value   $ 6.55  
Risk-free interest rate, minimum 1.40% 2.60% 1.90%
Risk-free interest rate, maximum 2.50% 3.00% 2.40%
Expected volatility, minimum 64.30% 65.00% 67.30%
Expected volatility, maximum 72.90% 69.20% 70.50%
Minimum      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Grant date fair value $ 7.80   $ 6.27
Expected term, minimum (in years) 5 years 3 months 7 days 6 years 29 days 6 years 29 days
Maximum      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Grant date fair value $ 47.81   $ 6.32
Expected term, minimum (in years) 6 years 29 days 10 years 10 years