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Stock-Based Compensation - Assumptions Used to Estimate Fair Value of Stock Options (Details)
9 Months Ended
Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Risk-free interest rate, minimum 0.50%
Risk-free interest rate, maximum 0.90%
Volatility, minimum 64.40%
Volatility, maximum 80.80%
Dividend yield 0.00%
Minimum [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Expected life (years) 3 years 6 months
Maximum [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Expected life (years) 6 years 1 month 6 days