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Stock-based Compensation (Weighted Average Fair Values, Assumptions in Valuation Models for Options Granted) (Details) - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
31. Stock-Based Compensation    
Weighted average fair value per option $ 3.58 $ 2.41
Expected term 5 years 6 years
Risk-free interest rate 1.33% 1.82%
Expected dividend yield 4.09% 5.10%
Expected volatility 14.10% 14.32%