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Capital Stock (Option Grant Assumptions) (Details) - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Capital Stock [Abstract]      
Weighted-average fair value per share $ 36.30 $ 28.52 $ 22.43
Risk-free interest rate 2.60% 2.70% 2.00%
Expected dividend yield 1.10% 1.20% 1.50%
Expected stock price volatility 18.30% 16.80% 19.40%
Expected option life (years) 5 years 10 months 24 days 6 years 6 years