Pension And OPEB (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 24	$ 23	$ 47	$ 45
Interest Cost	56	69	112	138
Expected Return on Plan Assets	(81)	(96)	(161)	(191)
Amortization of Prior Service Cost	0	0	0	0
Amortization of Actuarial Loss	18	24	36	48
Non-Operating Pension and OPEB (Credits) Costs	(7)	(3)	(13)	(5)
Total Benefit (Credits) Costs	17	20	34	40
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0	1	1	2
Interest Cost	10	11	19	21
Expected Return on Plan Assets	(8)	(9)	(17)	(17)
Amortization of Prior Service Cost	1	(13)	1	(26)
Amortization of Actuarial Loss	(1)	0	(1)	(1)
Non-Operating Pension and OPEB (Credits) Costs	2	(11)	2	(23)
Total Benefit (Credits) Costs	$ 2	$ (10)	$ 3	$ (21)