Revenue from Contracts with Customers - MEC (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 4,745	$ 4,199	$ 9,464	$ 8,911
Operating revenue	6,612	6,064	12,642	12,145
Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	195	102	299	239
MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	862	690	1,849	1,752
Operating revenue	897	693	1,902	1,760
MEC | Other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1		2	11
MEC | Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	35	3	53	8
Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	3,989	3,587	8,104	7,681
Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	2,591	2,411	4,847	4,519
Regulated | Retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	164	109	552	607
Regulated | Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	187	108	423	301
Regulated | Other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	28	31	50	56
Regulated | MEC | Retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	730	605	1,539	1,517
Regulated | MEC | Retail | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	272	229	665	698
Regulated | MEC | Retail | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	122	98	284	298
Regulated | MEC | Retail | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	286	233	493	435
Regulated | MEC | Retail | Natural gas transportation services
Disaggregation of Revenue [Line Items]
Total Customer Revenue	9	9	23	19
Regulated | MEC | Retail | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	41	36	74	67
Regulated | MEC | Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	118	69	280	194
Regulated | MEC | Multi-value transmission projects | Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Total Customer Revenue	13	15	28	30
Nonregulated | MEC | Other
Disaggregation of Revenue [Line Items]
Total Customer Revenue		1
Regulated electric | MEC
Disaggregation of Revenue [Line Items]
Operating revenue	725	586	1,333	1,131
Regulated electric | Regulated | MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	691	583	1,282	1,124
Operating revenue	725	586	1,333	1,131
Regulated electric | Regulated | MEC | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	594	516	1,066	968
Regulated electric | Regulated | MEC | Retail electric | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	185	170	353	331
Regulated electric | Regulated | MEC | Retail electric | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	91	80	165	151
Regulated electric | Regulated | MEC | Retail electric | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	277	230	475	420
Regulated electric | Regulated | MEC | Retail electric | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	41	36	73	66
Regulated electric | Regulated | MEC | Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	84	52	188	126
Regulated electric | Regulated | MEC | Multi-value transmission projects | Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Total Customer Revenue	13	15	28	30
Regulated electric | Regulated | MEC | Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	34	3	51	7
Regulated natural gas | MEC
Disaggregation of Revenue [Line Items]
Operating revenue	171	106	567	618
Regulated natural gas | Regulated | MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	170	106	565	617
Operating revenue	171	106	567	618
Regulated natural gas | Regulated | MEC | Retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	136	89	473	549
Regulated natural gas | Regulated | MEC | Retail gas | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	87	59	312	367
Regulated natural gas | Regulated | MEC | Retail gas | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	31	18	119	147
Regulated natural gas | Regulated | MEC | Retail gas | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	9	3	18	15
Regulated natural gas | Regulated | MEC | Retail gas | Natural gas transportation services
Disaggregation of Revenue [Line Items]
Total Customer Revenue	9	9	23	19
Regulated natural gas | Regulated | MEC | Retail gas | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	0	0	1	1
Regulated natural gas | Regulated | MEC | Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	34	17	92	68
Regulated natural gas | Regulated | MEC | Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	1	0	2	1
Other | MEC
Disaggregation of Revenue [Line Items]
Operating revenue	1	1	2	11
Other | Nonregulated | MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	1	2	11
Operating revenue	1	1	2	11
Other | Nonregulated | MEC | Other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	1	2	11
Other | Nonregulated | MEC | Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	$ 0	$ 0	$ 0	$ 0