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Stock-Based Compensation Expense - Schedule of Assumptions Used to Value Options Granted (Parenthetical) (Details) - shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares, options granted 0 0 0
Performance Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares, options granted   0 0