Revenue from Contracts with Customers - MEC (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Operating revenue	$ 6,229	$ 6,612	$ 12,575	$ 12,642
MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	725	862	1,629	1,849
Other revenue	34	35	50	53
Operating revenue	759	897	1,679	1,902
MEC | Other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1		4	2
Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	2,844	2,591	5,532	4,847
Regulated | Retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	133	164	525	552
Regulated | Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	89	187	280	423
Regulated | Other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	23	28	57	50
Regulated | MEC | Retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	659	730	1,446	1,539
Regulated | MEC | Retail | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	231	272	597	665
Regulated | MEC | Retail | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	103	122	256	284
Regulated | MEC | Retail | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	276	286	497	493
Regulated | MEC | Retail | Natural gas transportation services
Disaggregation of Revenue [Line Items]
Total Customer Revenue	10	9	23	23
Regulated | MEC | Retail | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	39	41	73	74
Regulated | MEC | Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	52	118	152	280
Regulated | MEC | Multi-value transmission projects | Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Total Customer Revenue	13	13	27	28
Nonregulated | MEC | Other
Disaggregation of Revenue [Line Items]
Total Customer Revenue		1
Regulated electric | MEC
Disaggregation of Revenue [Line Items]
Operating revenue	661	725	1,252	1,333
Regulated electric | Regulated | MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	627	691	1,203	1,282
Other revenue	34	34	49	51
Operating revenue	661	725	1,252	1,333
Regulated electric | Regulated | MEC | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	569	594	1,060	1,066
Regulated electric | Regulated | MEC | Retail electric | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	173	185	340	353
Regulated electric | Regulated | MEC | Retail electric | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	86	91	161	165
Regulated electric | Regulated | MEC | Retail electric | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	272	277	486	475
Regulated electric | Regulated | MEC | Retail electric | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	38	41	73	73
Regulated electric | Regulated | MEC | Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	45	84	116	188
Regulated electric | Regulated | MEC | Multi-value transmission projects | Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Total Customer Revenue	13	13	27	28
Regulated natural gas | MEC
Disaggregation of Revenue [Line Items]
Operating revenue	97	171	423	567
Regulated natural gas | Regulated | MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	97	170	422	565
Other revenue	0	1	1	2
Operating revenue	97	171	423	567
Regulated natural gas | Regulated | MEC | Retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	90	136	386	473
Regulated natural gas | Regulated | MEC | Retail gas | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	58	87	257	312
Regulated natural gas | Regulated | MEC | Retail gas | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	17	31	95	119
Regulated natural gas | Regulated | MEC | Retail gas | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	4	9	11	18
Regulated natural gas | Regulated | MEC | Retail gas | Natural gas transportation services
Disaggregation of Revenue [Line Items]
Total Customer Revenue	10	9	23	23
Regulated natural gas | Regulated | MEC | Retail gas | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	0	0	1
Regulated natural gas | Regulated | MEC | Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	7	34	36	92
Other | MEC
Disaggregation of Revenue [Line Items]
Operating revenue	1	1	4	2
Other | Nonregulated | MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	1	4	2
Other revenue	0	0	0	0
Operating revenue	1	1	4	2
Other | Nonregulated | MEC | Other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 1	$ 1	$ 4	$ 2