Revenue from Contracts with Customers - MEC (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Operating revenue	$ 6,672	$ 6,366
MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1,123	986
Other revenue	17	28
Operating revenue	1,140	1,014
MEC \| Other customer revenue
Disaggregation of Revenue [Line Items]
Total Customer Revenue	3	2
Regulated \| Regulated retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	2,968	2,824
Regulated \| Regulated retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	369	358
Regulated \| Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	223	146
Regulated \| Other customer revenue
Disaggregation of Revenue [Line Items]
Total Customer Revenue	46	27
Regulated \| MEC \| Retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	921	854
Regulated \| MEC \| Retail \| Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	398	383
Regulated \| MEC \| Retail \| Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	170	160
Regulated \| MEC \| Retail \| Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	302	260
Regulated \| MEC \| Retail \| Natural gas transportation services
Disaggregation of Revenue [Line Items]
Total Customer Revenue	16	16
Regulated \| MEC \| Retail \| Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	35	35
Regulated \| MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	186	116
Regulated \| MEC \| Multi-value transmission projects \| Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Total Customer Revenue	13	14
Electric \| Regulated \| MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	730	639
Other revenue	17	28
Operating revenue	747	667
Electric \| Regulated \| MEC \| Regulated retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	589	545
Electric \| Regulated \| MEC \| Regulated retail electric \| Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	181	181
Electric \| Regulated \| MEC \| Regulated retail electric \| Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	82	80
Electric \| Regulated \| MEC \| Regulated retail electric \| Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	293	251
Electric \| Regulated \| MEC \| Regulated retail electric \| Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	33	33
Electric \| Regulated \| MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	128	80
Electric \| Regulated \| MEC \| Multi-value transmission projects \| Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Total Customer Revenue	13	14
Natural Gas \| Regulated \| MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	390	345
Other revenue	0	0
Operating revenue	390	345
Natural Gas \| Regulated \| MEC \| Regulated retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	332	309
Natural Gas \| Regulated \| MEC \| Regulated retail gas \| Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	217	202
Natural Gas \| Regulated \| MEC \| Regulated retail gas \| Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	88	80
Natural Gas \| Regulated \| MEC \| Regulated retail gas \| Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	9	9
Natural Gas \| Regulated \| MEC \| Regulated retail gas \| Natural gas transportation services
Disaggregation of Revenue [Line Items]
Total Customer Revenue	16	16
Natural Gas \| Regulated \| MEC \| Regulated retail gas \| Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	2	2
Natural Gas \| Regulated \| MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Total Customer Revenue	58	36
Other \| Nonregulated \| MEC
Disaggregation of Revenue [Line Items]
Total Customer Revenue	3	2
Other revenue	0	0
Operating revenue	3	2
Other \| Nonregulated \| MEC \| Other customer revenue
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 3	$ 2

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