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Stock-Based Compensation - Assumptions Used For Stock Options (Details) - Stock option awards - $ / shares
6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted average grant-date fair value per share (in dollars per share) $ 0 $ 1.16
Expected term (in years) 0 years 6 years
Expected stock volatility 0.00% 86.00%
Dividend yield 0.00% 0.00%
Risk-free interest rate 0.00% 1.00%