Employee Benefit Plans (Schedule Of Estimated Benefits Expected To Be Paid) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
2018	$ 712
2019	811
2020	850
2021	886
2022	920
Thereafter in the succeeding five years	5,002
Employer contribution	335	$ 334
Expected employer contribution next year	327
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2018	83
2019	87
2020	91
2021	95
2022	100
Thereafter in the succeeding five years	508
Employer contribution	33	$ 52
Expected employer contribution next year	24
Federal Subsidy [Member]
Defined Benefit Plan Disclosure [Line Items]
2018	(8)
2019	(9)
2020	(9)
2021	(10)
2022	(3)
Thereafter in the succeeding five years	$ (15)