Income Taxes - NPC - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	$ 1,290	$ 1,248
Other	649	629
Total deferred income tax assets	3,406	3,400
Property-related items	(12,949)	(12,596)
Regulatory assets	(1,124)	(1,034)
Other	(378)	(491)
Total deferred income tax liabilities	(15,956)	(15,695)
Net deferred income tax liability	(12,628)	(12,437)
NPC
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	201	195
Operating and finance leases	62	66
Customer advances	44	38
Derivative contracts and unamortized contract values	12	14
Other	8	9
Total deferred income tax assets	327	322
Property-related items	(884)	(828)
Regulatory assets	(163)	(245)
Operating and finance leases	(59)	(62)
Other	(23)	(23)
Total deferred income tax liabilities	(1,129)	(1,158)
Net deferred income tax liability	$ (802)	$ (836)