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Stock-Based Compensation - Valuation Assumptions (Details) - Stock Options - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted average fair value of stock options granted $ 0 $ 0 $ 4.09
Volatility 0.00% 0.00% 66.86%
Expected life in years 0 years 0 years 4 years
Risk-free interest rate 0.00% 0.00% 2.07%
Dividend yield 0.00% 0.00% 0.00%