Stock-Based Compensation (Schedule Of Options) (Details) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Related tax benefit realized	$ 54	$ 31	$ 13
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	171,080	406,038	236,601
Common stock, shares, issued (in shares)	99,805	241,757	141,386
Related tax benefit realized	$ 1	$ 3	$ 3
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	137,200	175,500	166,750
Common stock, shares, issued (in shares)	81,318	103,936	99,337
Related tax benefit realized	$ 3	$ 1	$ 4