Segment Information - MEC (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) operatingSegment reportableSegment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment	8
Revenues	$ 25,150	$ 20,952	$ 19,844
Operating income (loss)	5,327	4,291	4,150
Interest expense	2,118	2,021	1,912
Income tax (benefit) expense	(1,132)	308	(598)
Net income attributable to parent	5,790	6,943	2,950
Capitalized expenditures	6,611	6,765	7,364
Assets	$ 132,065	127,316	100,051
MEC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment	2
Revenues	$ 3,547	2,720	2,925
Depreciation and amortization	914	716	639
Operating income (loss)	416	448	548
Interest expense	302	304	281
Income tax (benefit) expense	(675)	(570)	(371)
Net income attributable to parent	894	826	793
Capitalized expenditures	1,912	1,836	2,810
Assets	23,257	21,437	20,564
MEC | Other
Segment Reporting Information [Line Items]
Revenues	15	8	28
Operating income (loss)	0	0	4
Income tax (benefit) expense	(1)	0	1
Net income attributable to parent	0	1	2
Assets	1	1	3
MEC | Regulated electric | Operating segments
Segment Reporting Information [Line Items]
Revenues	2,529	2,139	2,237
Depreciation and amortization	861	667	593
Operating income (loss)	358	384	473
Interest expense	279	281	259
Income tax (benefit) expense	(677)	(584)	(384)
Net income attributable to parent	844	780	739
Capitalized expenditures	1,806	1,704	2,684
Assets	21,385	19,892	19,093
MEC | Regulated natural gas | Operating segments
Segment Reporting Information [Line Items]
Revenues	1,003	573	660
Depreciation and amortization	53	49	46
Operating income (loss)	58	64	71
Interest expense	23	23	22
Income tax (benefit) expense	3	14	12
Net income attributable to parent	50	45	52
Capitalized expenditures	106	132	126
Assets	$ 1,871	$ 1,544	$ 1,468