Revenue from Contract with Customer - MEC (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Total operating revenue	$ 25,150	$ 20,952	$ 19,844
MEC
Disaggregation of Revenue [Line Items]
Customer revenue	3,514	2,696	2,902
Other revenue	33	24	23
Total operating revenue	3,547	2,720	2,925
MEC \| Retail
Disaggregation of Revenue [Line Items]
Customer revenue	2,987	2,429	2,508
MEC \| Retail \| Residential
Disaggregation of Revenue [Line Items]
Customer revenue	1,282	1,027	1,055
MEC \| Retail \| Commercial
Disaggregation of Revenue [Line Items]
Customer revenue	550	415	454
MEC \| Retail \| Industrial
Disaggregation of Revenue [Line Items]
Customer revenue	964	818	816
MEC \| Retail \| Natural gas transportation services
Disaggregation of Revenue [Line Items]
Customer revenue	39	36	38
MEC \| Retail \| Other retail
Disaggregation of Revenue [Line Items]
Customer revenue	152	133	145
MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Customer revenue	454	199	309
MEC \| Multi-value transmission projects \| Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Customer revenue	58	60	57
MEC \| Other
Disaggregation of Revenue [Line Items]
Customer revenue	15	8	28
Regulated assets \| Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	9,801	9,421	9,465
Regulated assets \| Retail Gas
Disaggregation of Revenue [Line Items]
Customer revenue	974	619	686
Regulated assets \| Wholesale
Disaggregation of Revenue [Line Items]
Customer revenue	727	366	457
Regulated assets \| Other
Disaggregation of Revenue [Line Items]
Customer revenue	109	110	2
Regulated electric \| Regulated assets \| MEC
Disaggregation of Revenue [Line Items]
Customer revenue	2,498	2,117	2,216
Other revenue	31	22	21
Total operating revenue	2,529	2,139	2,237
Regulated electric \| Regulated assets \| MEC \| Retail Electric
Disaggregation of Revenue [Line Items]
Customer revenue	2,128	1,924	1,938
Regulated electric \| Regulated assets \| MEC \| Retail Electric \| Residential
Disaggregation of Revenue [Line Items]
Customer revenue	718	685	672
Regulated electric \| Regulated assets \| MEC \| Retail Electric \| Commercial
Disaggregation of Revenue [Line Items]
Customer revenue	327	304	322
Regulated electric \| Regulated assets \| MEC \| Retail Electric \| Industrial
Disaggregation of Revenue [Line Items]
Customer revenue	934	804	799
Regulated electric \| Regulated assets \| MEC \| Retail Electric \| Other retail
Disaggregation of Revenue [Line Items]
Customer revenue	149	131	145
Regulated electric \| Regulated assets \| MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Customer revenue	312	133	221
Regulated electric \| Regulated assets \| MEC \| Multi-value transmission projects \| Multi-value transmission projects
Disaggregation of Revenue [Line Items]
Customer revenue	58	60	57
Regulated natural gas \| Regulated assets \| MEC
Disaggregation of Revenue [Line Items]
Customer revenue	1,001	571	658
Other revenue	2	2	2
Total operating revenue	1,003	573	660
Regulated natural gas \| Regulated assets \| MEC \| Retail Gas
Disaggregation of Revenue [Line Items]
Customer revenue	859	505	570
Regulated natural gas \| Regulated assets \| MEC \| Retail Gas \| Residential
Disaggregation of Revenue [Line Items]
Customer revenue	564	342	383
Regulated natural gas \| Regulated assets \| MEC \| Retail Gas \| Commercial
Disaggregation of Revenue [Line Items]
Customer revenue	223	111	132
Regulated natural gas \| Regulated assets \| MEC \| Retail Gas \| Industrial
Disaggregation of Revenue [Line Items]
Customer revenue	30	14	17
Regulated natural gas \| Regulated assets \| MEC \| Retail Gas \| Natural gas transportation services
Disaggregation of Revenue [Line Items]
Customer revenue	39	36	38
Regulated natural gas \| Regulated assets \| MEC \| Retail Gas \| Other retail
Disaggregation of Revenue [Line Items]
Customer revenue	3	2	0
Regulated natural gas \| Regulated assets \| MEC \| Wholesale
Disaggregation of Revenue [Line Items]
Customer revenue	142	66	88
Other \| Nonregulated assets \| MEC
Disaggregation of Revenue [Line Items]
Customer revenue	15	8	28
Other revenue	0	0	0
Total operating revenue	15	8	28
Other \| Nonregulated assets \| MEC \| Other
Disaggregation of Revenue [Line Items]
Customer revenue	$ 15	$ 8	$ 28

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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