Income Taxes - NPC - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	$ 1,248	$ 1,323
Other	629	632
Total deferred income tax assets	3,400	3,159
Property-related items	(12,596)	(12,244)
Regulatory assets	(1,034)	(898)
Other	(491)	(510)
Total deferred income tax liabilities	(15,695)	(15,650)
Net deferred income tax liability	(12,437)	(12,678)
NPC
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	195	186
Operating and finance leases	66	68
Customer advances	38	27
Derivative contracts and unamortized contract values	14	20
Other	9	9
Total deferred income tax assets	322	310
Property-related items	(828)	(821)
Regulatory assets	(245)	(273)
Operating and finance leases	(62)	(65)
Other	(23)	(26)
Total deferred income tax liabilities	(1,158)	(1,185)
Net deferred income tax liability	$ (836)	$ (875)