Retirement Benefits (Schedule Of Accumulated And Projected Benefit Obligations) (Details) - DB Pension Plans [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Pension PBO	$ 2,780	$ 2,562	$ 2,403
Pension ABO	2,400	2,250
Fair value of plan assets	2,305	$ 2,101	$ 2,013
Pension Plan A [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension PBO	1,511
Pension ABO	1,164
Fair value of plan assets	$ 893