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Stock-Based Compensation Plans (Details 5) - Performance awards - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]      
Dividend yield (as a percent) 3.70% 3.20% 3.30%
Estimated volatility, minimum (as a percent) 11.80% 15.30% 15.20%
Estimated volatility, maximum (as a percent) 18.70% 19.70% 22.80%
Risk-free interest rate, minimum (as a percent) 1.86% 0.69% 0.44%
Risk-free interest rate, maximum (as a percent) 2.46% 1.61% 0.88%
Estimated performance award value based on total shareholder return measure (in dollars per share) $ 151.67 $ 175.86 $ 131.24
Historical volatility (as a percent) 50.00% 50.00% 50.00%
Implied volatility (as a percent) 50.00% 50.00% 50.00%
Market closing price (in dollars per share) $ 161.10 $ 179.07 $ 161.66