Pension And OPEB (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 36	$ 38	$ 71	$ 76
Interest Cost	41	35	83	70
Expected Return on Plan Assets	(121)	(119)	(242)	(238)
Amortization of Prior Service Cost	0	0	0	0
Amortization of Actuarial Loss	15	25	30	51
Non-Operating Pension and OPEB (Credits) Costs	(65)	(59)	(129)	(117)
Total Benefit (Credits) Costs	(29)	(21)	(58)	(41)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	1	2	3	4
Interest Cost	7	6	13	11
Expected Return on Plan Assets	(10)	(11)	(21)	(21)
Amortization of Prior Service Cost	(32)	(32)	(64)	(64)
Amortization of Actuarial Loss	3	11	7	22
Non-Operating Pension and OPEB (Credits) Costs	(32)	(26)	(65)	(52)
Total Benefit (Credits) Costs	$ (31)	$ (24)	$ (62)	$ (48)