Pension, OPEB and Savings Plans (Pre-Tax Changes Recognized In Accumulated Other Comprehensive Income (Loss), Regulatory Assets And Deferred Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Actuarial (Gain) Loss in Current Period	$ 296	$ 241
Amortization of Net Actuarial Gain (Loss)	(92)	(96)
Prior Service Cost (Credit) in Current Period	0	0
Amortization of Prior Service Credit	10	18
Total	214	163
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Actuarial (Gain) Loss in Current Period	2	39
Amortization of Net Actuarial Gain (Loss)	(47)	(50)
Prior Service Cost (Credit) in Current Period	(5)	0
Amortization of Prior Service Credit	128	128
Total	$ 78	$ 117