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Stock Based Compensation (Weighted Average Assumptions Used to Value Option Grants) (Details) - Employee Stock Option
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate (%) 0.94% 0.83%
Expected option life (years) 5 years 7 months 9 days 5 years 7 months 20 days
Expected volatility (%) 25.16% 20.18%
Expected dividend yield (%) 0.56% 0.62%