Segment Information - MEC (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) operatingSegment reportableSegment	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment	8
Operating revenue	$ 6,346	$ 6,030
Operating income (loss)	667	1,236
Interest expense	(586)	(532)
Allowance for equity funds	49	38
Other, net	40	5
Income (loss) before income tax expense (benefit) and equity income (loss)	979	(470)
Assets	$ 134,454		$ 133,840
MEC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment	2
Operating revenue	$ 920	1,005
Operating income (loss)	88	100
Interest expense	(80)	(78)
Allowance for borrowed funds	4	4
Allowance for equity funds	11	15
Other, net	16	(3)
Income (loss) before income tax expense (benefit) and equity income (loss)	39	38
Assets	23,807		23,978
MEC | Regulated electric
Segment Reporting Information [Line Items]
Operating revenue	591	608
Operating income (loss)	50	51
Assets	22,091		22,092
MEC | Regulated natural gas
Segment Reporting Information [Line Items]
Operating revenue	326	396
Operating income (loss)	38	49
Assets	1,716		1,885
MEC | Other
Segment Reporting Information [Line Items]
Operating revenue	3	$ 1
Assets	$ 0		$ 1