Regulatory Matters - MEC - Regulatory Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Feb. 28, 2021
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 7,070	$ 6,960
Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	27 years
Revenue sharing mechanisms
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	2 years
Asset retirement obligations
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	31 years
MEC
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,119	1,080
Adjustment clause, under (over) collection in receivables	$ 156	230	$ 245
MEC | Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	29 years
Regulatory liabilities	$ 392	394
MEC | Revenue sharing mechanisms
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	1 year
Regulatory liabilities	$ 312	115
MEC | Asset retirement obligations
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	31 years
Regulatory liabilities	$ 247	341
MEC | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 72	83
MEC | Pre-funded AFUDC on transmission MVPs
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	57 years
Regulatory liabilities	$ 34	34
MEC | Unrealized gain on regulated derivatives
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	1 year
Regulatory liabilities	$ 31	26
MEC | Employee benefit plans
Regulatory Liabilities [Line Items]
Regulatory liabilities	0	55
MEC | Other
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 31	$ 32