Share-Based Compensation (Schedule Of Aggregate Fair Value Of Restricted Stock, Performance-Based Restricted Stock And Performance Shares, Awards And Units, That Vested During The Period) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restricted Stock Awards And Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate fair value of awards and units, vested	$ 73	$ 101	$ 112
Performance-Based Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate fair value of awards and units, vested	5	8	$ 10
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate fair value of awards and units, vested	$ 13	$ 22