Pension, OPEB and Savings Plans (Amounts Expected To Be Amortized From Accumulated OCL, Regulatory Assets And Deferred Assets Into Net Periodic Benefit Cost) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial (Gain) Loss	$ 85
Prior Service Cost	(18)
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial (Gain) Loss	64
Prior Service Cost	$ (1)