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Stock-Based Incentive Compensation Plans (Option price assumptions used for stock option incentive plans) (Details) - Stock options [Member] - $ / shares
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Assumptions used for stock-based incentive compensation plans [Abstract]      
Weighted-average fair value per option granted (in dollars per share) $ 18.27 $ 9.32 $ 13.00
Dividend yield 2.00% 2.80% 1.90%
Expected volatility 31.50% 35.90% 28.00%
Risk-free interest rate, minimum 1.70% 1.00% 1.40%
Risk-free interest rate, maximum 2.10% 1.60% 1.70%
Expected life (in years) 5 years 6 months 5 years 8 months 12 days 5 years 6 months