Pension And OPEB (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 23	$ 36	$ 45	$ 71
Interest Cost	69	41	138	83
Expected Return on Plan Assets	(96)	(121)	(191)	(242)
Amortization of Prior Service Cost	0	0	0	0
Amortization of Actuarial Loss	24	15	48	30
Non-Operating Pension and OPEB (Credits) Costs	(3)	(65)	(5)	(129)
Total Benefit (Credits) Costs	20	(29)	40	(58)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1	1	2	3
Interest Cost	11	7	21	13
Expected Return on Plan Assets	(9)	(10)	(17)	(21)
Amortization of Prior Service Cost	(13)	(32)	(26)	(64)
Amortization of Actuarial Loss	0	3	(1)	7
Non-Operating Pension and OPEB (Credits) Costs	(11)	(32)	(23)	(65)
Total Benefit (Credits) Costs	$ (10)	$ (31)	$ (21)	$ (62)