Stock-Based Compensation (Stock Option Weighted-Average Assumptions Used In Determining Fair Values) (Details) - Employee Stock Option [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock price volatility	18.39%	20.38%	23.62%
Expected term	7 years 128 days	7 years 90 days	7 years 22 days
Risk-free interest rate	2.31%	1.77%	1.59%
Dividend yield	4.75%	4.50%	4.50%
Dividend payment per share	$ 3.50	$ 3.42	$ 3.34