Stock-Based Incentive Compensation Plans (Compensation Expense By Award Type) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	$ 50	$ 46	$ 41
Recognized tax benefit	18	16	14
Stock options [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	10	9	7
Performance Shares [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	13	11	12
Non-employee Stock Appreciation Rights [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	2	3
Restricted Stock Units And Non-Vested Stock [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	$ 25	$ 23	$ 22