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Stock-Based Compensation - Estimated Fair Value of Option on Grant Date using Weighted Average Assumptions (Details) - Employee Stock Option - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 1.37% 2.36%
Expected term (in years) 6 years 5 years 10 months 24 days
Expected volatility 71.00% 69.00%
Expected dividend yield 0.00% 0.00%
Fair value of common stock (in usd per share) $ 5.09 $ 4.19