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Share-Based Payments (Weighted Average Assumptions for Employee Stock Purchase Plan and Other Options) (Details) - Employee Stock Purchase Plan [Member]
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Risk-free interest rate 0.76% 2.33% 1.88%
Expected term 6 months 6 months 6 months
Dividend yield 1.60% 1.20% 1.30%
Expected volatility 37.00% 26.00% 18.00%