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Stock-Based Compensation - Employee Stock Purchase Plan (Details) - ESPP - $ / shares
6 Months Ended
Jun. 30, 2022
Jun. 30, 2021
Fair Value    
Risk-free interest rate, minimum 0.60%  
Risk-free interest rate, maximum 1.40% 0.10%
Dividend yield 0.00% 0.00%
Volatility, minimum 116.20% 120.40%
Volatility, maximum 142.90% 159.40%
Minimum    
Fair Value    
Range of Black-Scholes fair values of ESPP shares granted (in usd per share) $ 44.67 $ 128.70
Expected term (in years) 6 months 6 months
Maximum    
Fair Value    
Range of Black-Scholes fair values of ESPP shares granted (in usd per share) $ 79.74 $ 238.85
Expected term (in years) 2 years 2 years