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Stock-Based Compensation - Valuation Assumptions (Details) - $ / shares
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Valuation Assumptions        
Granted (in shares) 0 0   0
Stock options        
Valuation Assumptions        
Expected term (in years)     6 years  
Volatility     45.00%  
Dividend yield     0.00%  
Stock options | Weighted-average        
Valuation Assumptions        
Weighted-average estimated fair value of shares granted (in dollars per share)     $ 5.61  
Stock options | Minimum        
Valuation Assumptions        
Risk-free interest rate     1.07%  
Stock options | Maximum        
Valuation Assumptions        
Risk-free interest rate     1.13%