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Capital Stock and Stock-Based Compensation Plans - Fair Value Assumptions (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Payment Arrangement [Abstract]      
Expected term of options 6 years 6 years 4 years 6 months
Expected volatility rate 21.80% 19.20% 17.70%
Risk-free interest rate 0.50% 1.50% 2.80%
Expected dividend yield 2.30% 2.30% 2.50%