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Stock-Based Compensation - Fair Value of Employee Option Grant Estimated on Date of Grant (Details) - Outstanding options to purchase common stock - $ / shares
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award    
Estimated weighted-average fair value (USD per share) $ 11.29 $ 12.79
Weighted Average    
Weighted-average assumptions    
Expected volatility 81.00% 81.00%
Expected life, in years 6 years 1 month 6 days 6 years 1 month 6 days
Risk-free interest rate 0.98% 0.89%
Expected dividend yield 0.00% 0.00%