Revenue from Contract with Customer - MEC (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Total operating revenue	$ 25,920	$ 25,602	$ 26,337
MEC
Disaggregation of Revenue [Line Items]
Customer revenue	3,174	3,311	3,911
Other revenue	77	82	114
Total operating revenue	3,251	3,393	4,025
MEC \| Retail
Disaggregation of Revenue [Line Items]
Customer revenue	2,891	2,947	3,175
MEC \| Retail \| Residential
Disaggregation of Revenue [Line Items]
Customer revenue	1,121	1,155	1,320
MEC \| Retail \| Commercial
Disaggregation of Revenue [Line Items]
Customer revenue	471	496	570
MEC \| Retail \| Industrial
Disaggregation of Revenue [Line Items]
Customer revenue	1,086	1,095	1,085
MEC \| Retail \| Natural gas transportation services
Disaggregation of Revenue [Line Items]
Customer revenue	51	46	44
MEC \| Retail \| Other retail
Disaggregation of Revenue [Line Items]
Customer revenue	162	155	156
MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Customer revenue	221	303	668
MEC \| Multi-value transmission projects \| Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Customer revenue	53	54	61
MEC \| Other
Disaggregation of Revenue [Line Items]
Customer revenue	9	7	7
Regulated assets \| Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	12,259	11,891	10,884
Regulated assets \| Retail Gas
Disaggregation of Revenue [Line Items]
Customer revenue	785	873	1,022
Regulated assets \| Wholesale
Disaggregation of Revenue [Line Items]
Customer revenue	361	553	1,024
Regulated assets \| Other
Disaggregation of Revenue [Line Items]
Customer revenue	126	136	105
Electric \| Regulated assets \| MEC
Disaggregation of Revenue [Line Items]
Customer revenue	2,508	2,593	2,876
Other revenue	76	80	112
Total operating revenue	2,584	2,673	2,988
Electric \| Regulated assets \| MEC \| Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	2,287	2,309	2,320
Electric \| Regulated assets \| MEC \| Retail Electric \| Residential
Disaggregation of Revenue [Line Items]
Customer revenue	729	735	765
Electric \| Regulated assets \| MEC \| Retail Electric \| Commercial
Disaggregation of Revenue [Line Items]
Customer revenue	333	344	354
Electric \| Regulated assets \| MEC \| Retail Electric \| Industrial
Disaggregation of Revenue [Line Items]
Customer revenue	1,069	1,075	1,047
Electric \| Regulated assets \| MEC \| Retail Electric \| Other retail
Disaggregation of Revenue [Line Items]
Customer revenue	156	155	154
Electric \| Regulated assets \| MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Customer revenue	168	230	495
Electric \| Regulated assets \| MEC \| Multi-value transmission projects \| Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Customer revenue	53	54	61
Natural Gas \| Regulated assets \| MEC
Disaggregation of Revenue [Line Items]
Customer revenue	657	711	1,028
Other revenue	1	2	2
Total operating revenue	658	713	1,030
Natural Gas \| Regulated assets \| MEC \| Retail Gas
Disaggregation of Revenue [Line Items]
Customer revenue	604	638	855
Natural Gas \| Regulated assets \| MEC \| Retail Gas \| Residential
Disaggregation of Revenue [Line Items]
Customer revenue	392	420	555
Natural Gas \| Regulated assets \| MEC \| Retail Gas \| Commercial
Disaggregation of Revenue [Line Items]
Customer revenue	138	152	216
Natural Gas \| Regulated assets \| MEC \| Retail Gas \| Industrial
Disaggregation of Revenue [Line Items]
Customer revenue	17	20	38
Natural Gas \| Regulated assets \| MEC \| Retail Gas \| Natural gas transportation services
Disaggregation of Revenue [Line Items]
Customer revenue	51	46	44
Natural Gas \| Regulated assets \| MEC \| Retail Gas \| Other retail
Disaggregation of Revenue [Line Items]
Customer revenue	6	0	2
Natural Gas \| Regulated assets \| MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Customer revenue	53	73	173
Other \| Nonregulated assets \| MEC
Disaggregation of Revenue [Line Items]
Customer revenue	9	7	7
Other revenue	0	0	0
Total operating revenue	9	7	7
Other \| Nonregulated assets \| MEC \| Other
Disaggregation of Revenue [Line Items]
Customer revenue	$ 9	$ 7	$ 7

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