Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions		Dec. 31, 2024	Dec. 31, 2023
Deferred tax liabilities
Property related		$ 1,314	$ 1,227
Deferred fuel		5	23
Pension and postretirement benefits		123	100
Storm reserve		95	2
Total deferred tax liabilities		1,537	1,352
Deferred tax assets
Loss and credit carryforwards	[1]	438	383
Medical benefits		22	19
Insurance reserves		2	3
Pension and postretirement benefits		62	49
Other		37	18
Total deferred tax assets		561	472
Total deferred tax liability, net		$ 976	$ 880

[1] Deferred tax assets for net operating loss and tax credit carryforwards have been reduced by unrecognized tax benefits of $10 million and $10 million at December 31, 2024 and 2023, respectively.