Pension, OPEB and Savings Plans (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 151	$ 141	$ 123
Interest Cost	140	192	218
Expected Return on Plan Assets	(476)	(443)	(408)
Amortization of Prior Service Cost	0	(10)	(18)
Amortization of Net Actuarial Gain (Loss)	103	92	96
Non-Operating Pension and Other Postretirement Plan (Credits) Costs	(233)	(169)	(112)
Net Periodic Benefit Cost	(82)	(28)	11
Total Benefit Costs, Including Effect of Regulatory Asset	(82)	(28)	11
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	9	9	10
Interest Cost	22	34	45
Expected Return on Plan Assets	(42)	(39)	(36)
Amortization of Prior Service Cost	(129)	(128)	(128)
Amortization of Net Actuarial Gain (Loss)	44	47	50
Non-Operating Pension and Other Postretirement Plan (Credits) Costs	(105)	(86)	(69)
Net Periodic Benefit Cost	(96)	(77)	(59)
Total Benefit Costs, Including Effect of Regulatory Asset	$ (96)	$ (77)	$ (59)