Segment Information - MEC (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) reportableSegment operatingSegment	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment			8
Operating revenue	$ 7,500	$ 6,968	$ 20,142	$ 19,113
Operating income	1,823	1,834	4,266	4,375
Interest expense	(555)	(531)	(1,637)	(1,593)
Allowance for equity funds	43	34	123	90
Other, net	5	8	(16)	64
(Loss) income before income tax benefit and equity loss	(1,895)	1,675	884	4,189
Assets	132,004		$ 132,004		$ 132,065
MEC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment			2
Operating revenue	1,148	966	$ 3,050	2,726
Operating income	230	287	420	438
Interest expense	(79)	(76)	(235)	(224)
Allowance for borrowed funds	3	4	12	8
Allowance for equity funds	12	11	41	25
Other, net	4	8	(11)	34
(Loss) income before income tax benefit and equity loss	170	234	227	281
Assets	24,036		24,036		23,257
MEC | Regulated electric
Segment Reporting Information [Line Items]
Operating revenue	1,009	854	2,342	1,985
Operating income	245	289	383	401
Assets	22,195		22,195		21,385
MEC | Regulated natural gas
Segment Reporting Information [Line Items]
Operating revenue	138	110	705	728
Operating income	(15)	(2)	37	37
Assets	1,841		1,841		1,871
MEC | Other
Segment Reporting Information [Line Items]
Operating revenue	1	$ 2	3	$ 13
Assets	$ 0		$ 0		$ 1