Regulatory Matters - MEC - Regulatory Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 6,754	$ 6,644
Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	27 years
Asset retirement obligations
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	29 years
MEC
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,264	1,079
MEC | Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	28 years
Regulatory liabilities	$ 452	411
MEC | Asset retirement obligations
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	29 years
Regulatory liabilities	$ 443	360
MEC | Revenue sharing mechanisms
Regulatory Liabilities [Line Items]
Regulatory liabilities	186	127
MEC | Employee benefit plans
Regulatory Liabilities [Line Items]
Regulatory liabilities	73	16
MEC | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 47	102
MEC | Pre-funded AFUDC on transmission MVPs
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	55 years
Regulatory liabilities	$ 33	32
MEC | Other
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 30	$ 31