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Income Taxes (Details)
9 Months Ended 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Taxes          
Effective tax rate (3.50%) (1.10%) (1.20%) (0.60%) (0.60%)