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Stock-Based Compensation - Assumptions (Details)
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Fair value assumptions    
Expected term 6 years 1 month 6 days 6 years 1 month 6 days
Expected volatility 79.70% 69.70%
Expected dividend yield 0.00% 0.00%
Minimum    
Fair value assumptions    
Risk free interest rate 0.80% 0.60%
Maximum    
Fair value assumptions    
Risk free interest rate 1.40% 1.00%