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, 2016	Dec. 31, 2015
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Actuarial (Gain) Loss in Current Period	$ 211	$ 136
Amortization of Net Actuarial Gain (Loss)	(158)	(150)
Prior Service Cost (Credit) in current period	1	0
Amortization of Prior Service Credit	19	19
Total	73	5
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Actuarial (Gain) Loss in Current Period	125	(14)
Amortization of Net Actuarial Gain (Loss)	(40)	(43)
Prior Service Cost (Credit) in current period	(3)	0
Amortization of Prior Service Credit	14	14
Total	$ 96	$ (43)