Income Taxes (Schedule of Deferred Income Taxes) (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred income taxes:
Total deferred income tax assets	$ 728	$ 892
Total deferred income tax liabilities	2,033	2,107
Total net deferred income tax liabilities	1,305	1,215
Depreciation method and plant basis differences	1,203	1,164
Excess deferred income taxes	(212)	(219)
Unrecovered nuclear plant cost	450	479
DESC rate refund	(67)	(89)
Toshiba Settlement	(147)	(162)
Nuclear decommissioning	(51)	(44)
Deferred state income taxes	274	275
Federal benefit of deferred state income taxes	(60)	(60)
Deferred fuel, purchased energy and gas costs	32	107
Pension benefits	35	51
Other postretirement benefits	(17)	(32)
Loss and credit carryforwards	(185)	(313)
Other	50	58
Deferred investment tax credits	13	15
Total deferred taxes and deferred investment tax credits	$ 1,318	$ 1,230