Stock-Based Compensation Plans (Schedule of Weighted-Average Assumptions) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	2.10%	2.20%	2.10%
Expected volatility	26.70%	33.20%	35.80%
Risk-free interest rate	2.00%	1.40%	1.50%
Expected term of options (in years)	4 years 2 months 12 days	4 years 8 months 12 days	4 years 3 months 18 days
Weighted-average grant-date fair value (in dollars per share)	$ 4	$ 4	$ 4
Non-Employee Director Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	2.20%	2.20%	2.10%
Expected volatility	28.30%	34.10%	36.30%
Risk-free interest rate	2.20%	1.90%	2.20%
Expected term of options (in years)	6 years 4 months 24 days	6 years 2 months 12 days	6 years
Weighted-average grant-date fair value (in dollars per share)	$ 5	$ 4	$ 5