Pension And OPEB (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 22	$ 35
Interest Cost	69	42
Expected Return on Plan Assets	(95)	(121)
Amortization of Prior Service Cost	0	0
Amortization of Actuarial Loss	24	15
Non-Operating Pension and OPEB (Credits) Costs	(2)	(64)
Total Benefit (Credits) Costs	20	(29)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1	2
Interest Cost	10	6
Expected Return on Plan Assets	(8)	(11)
Amortization of Prior Service Cost	(13)	(32)
Amortization of Actuarial Loss	(1)	4
Non-Operating Pension and OPEB (Credits) Costs	(12)	(33)
Total Benefit (Credits) Costs	$ (11)	$ (31)