Employee Benefit Plans (AOCI and Regulatory Assets and Liabilities that have Not been Recognized as Components of Periodic Benefit (Credit) Cost) (Detail) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)		$ 1,506	$ 1,572
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)		3,018	2,714
Prior service (credit) cost		5	3
Total	[1]	3,023	2,717
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)		(35)	84
Prior service (credit) cost		(121)	(157)
Total	[1]	$ (156)	$ (73)

[1] As of December 31, 2023, of the $3.0 billion and $(156) million related to pension benefits and other postretirement benefits, $1.8 billion and $(38) million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities, except for $173 million presented in assets and liabilities held for sale. As of December 31, 2022, of the $2.7 billion and $(73) million related to pension benefits and other postretirement benefits, $1.7 billion and $14 million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities, except for $170 million presented in assets and liabilities held for sale.