Pension And OPEB (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Pension Lift Out Settlement Charge	$ 332		$ 332
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	23	$ 35	68	$ 106
Interest Cost	62	42	200	125
Expected Return on Plan Assets	(87)	(120)	(278)	(362)
Amortization of Prior Service Cost	0	0	0	0
Amortization of Actuarial Loss	19	15	67	45
Pension Lift Out Settlement Charge	332	0	332	0
Non-Operating Pension and OPEB (Credits) Costs	326	(63)	321	(192)
Total Benefit (Credits) Costs	349	(28)	389	(86)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1	2	3	5
Interest Cost	10	6	31	19
Expected Return on Plan Assets	(8)	(11)	(25)	(32)
Amortization of Prior Service Cost	(13)	(32)	(39)	(96)
Amortization of Actuarial Loss	(1)	4	(2)	11
Pension Lift Out Settlement Charge	0	0	0	0
Non-Operating Pension and OPEB (Credits) Costs	(12)	(33)	(35)	(98)
Total Benefit (Credits) Costs	$ (11)	$ (31)	$ (32)	$ (93)