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Share-Based Compensation - Valuation Assumptions (Details) - Stock Options
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Valuation Assumptions    
Expected volatility - minimum 75.00% 74.00%
Expected volatility - maximum 79.00% 74.00%
Weighted Average volatility 75.00% 74.00%
Expected dividend yield 0.00% 0.00%
Risk-free interest rate - minimum 0.40% 2.35%
Risk-free interest rate - maximum 1.71% 2.62%
Minimum    
Valuation Assumptions    
Expected term (in years) 6 years 6 years
Maximum    
Valuation Assumptions    
Expected term (in years) 6 years 6 years