Stock-Based Incentive Compensation Plans (Option price assumptions used for stock appreciation rights plan) (Details) - Non-employee Stock Appreciation Rights [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)	$ 20.06	$ 10.25	$ 14.22
Dividend yield	1.50%	2.90%	1.60%
Expected volatility	34.40%	35.80%	29.80%
Risk-free interest rate	2.20%	1.40%	1.80%
Expected life (in years)	5 years	5 years	5 years