Segment Information - MEC (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) operatingSegment reportableSegment	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment	8
Operating revenue	$ 6,111	$ 6,346
Operating income (loss)	895	667
Interest expense	(691)	(586)
Allowance for equity funds	83	49
Other, net	31	40
Income before income tax expense (benefit) and equity income (loss)	357	979
Assets	$ 140,235		$ 137,840
MEC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment	2
Operating revenue	$ 843	920
Operating income (loss)	76	88
Interest expense	(104)	(80)
Allowance for borrowed funds	6	4
Allowance for equity funds	16	11
Other, net	25	16
Income before income tax expense (benefit) and equity income (loss)	19	39
Assets	25,535		25,235
MEC | Regulated electric
Segment Reporting Information [Line Items]
Operating revenue	565	591
Operating income (loss)	31	50
Assets	23,635		23,334
MEC | Regulated natural gas
Segment Reporting Information [Line Items]
Operating revenue	276	326
Operating income (loss)	45	38
Assets	1,899		1,900
MEC | Other
Segment Reporting Information [Line Items]
Operating revenue	2	$ 3
Assets	$ 1		$ 1