Segment Information - MEC (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) reportableSegment operatingSegment	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment			8
Operating revenue	$ 6,612	$ 6,064	$ 12,642	$ 12,145
Operating income	1,207	1,208	2,443	2,541
Interest expense	(550)	(532)	(1,082)	(1,062)
Allowance for equity funds	42	30	80	56
Other, net	(26)	48	(21)	56
Income (loss) before income tax expense (benefit) and equity income (loss)	3,249	2,760	2,779	2,514
Assets	135,295		$ 135,295		$ 132,065
MEC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment			2
Operating revenue	897	693	$ 1,902	1,760
Operating income	90	103	190	151
Interest expense	(78)	(74)	(156)	(148)
Allowance for borrowed funds	5	2	9	4
Allowance for equity funds	14	8	29	14
Other, net	(12)	15	(15)	26
Income (loss) before income tax expense (benefit) and equity income (loss)	19	54	57	47
Assets	23,635		23,635		23,257
MEC | Regulated electric
Segment Reporting Information [Line Items]
Operating revenue	725	586	1,333	1,131
Operating income	87	103	138	112
Assets	21,967		21,967		21,385
MEC | Regulated natural gas
Segment Reporting Information [Line Items]
Operating revenue	171	106	567	618
Operating income	3	0	52	39
Assets	1,667		1,667		1,871
MEC | Other
Segment Reporting Information [Line Items]
Operating revenue	1	$ 1	2	$ 11
Assets	$ 1		$ 1		$ 1