Income Taxes - NPC - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	$ 1,323	$ 1,349
Other	741	686
Total deferred income tax assets	3,159	3,159
Property-related items	(12,244)	(11,814)
Regulatory assets	(898)	(764)
Other	(510)	(478)
Total deferred income tax liabilities	(15,650)	(15,933)
Net deferred income tax liability	(12,678)	(12,938)
NPC
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	186	195
Operating and finance leases	68	73
Customer advances	27	25
Derivative contracts and unamortized contract values	20	25
Other	9	8
Total deferred income tax assets	310	326
Property-related items	(821)	(800)
Regulatory assets	(273)	(204)
Operating and finance leases	(65)	(70)
Other	(26)	(34)
Total deferred income tax liabilities	(1,185)	(1,108)
Net deferred income tax liability	$ (875)	$ (782)