Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 7,929	$ 1,925
Mark-to-market for economic hedging activities	721	44
Operating revenues	8,091	2,019
Lease revenue	2	5
Derivative revenue	725	55
Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(3)	(2)
Operating revenues	(1)	(3)
Lease revenue	0	0
Retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6,162	1,661
Retail revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	(1)
Energy revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	482	124
Derivative revenue	58	53
Energy revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	(1)
Derivative revenue	2	(1)
Capacity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	155	149
Derivative revenue	37	24
Capacity revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Derivative revenue	0	0
Derivative revenue
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	(32)	(4)
Derivative revenue	160	89
Derivative revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	1	1
Derivative revenue	2	(1)
Other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,324	89
Other revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(3)	(2)
Total operating revenue
Disaggregation of Revenue [Line Items]
Operating revenues	8,091	2,019
Total operating revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(1)	(3)
Other revenue, derivative
Disaggregation of Revenue [Line Items]
Derivative revenue	97	16
Other revenue, derivative \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Derivative revenue	(1)	(1)
Home \| Retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,718	1,378
Home \| Retail revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	(1)
Business \| Retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,444	283
Business \| Retail revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Texas \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,609	1,351
Operating revenues	3,702	1,358
Lease revenue	0	0
Texas \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,114	1,292
Texas \| Energy revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	285	5
Derivative revenue	0	0
Texas \| Capacity revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Derivative revenue	0	0
Texas \| Derivative revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	(1)	0
Derivative revenue	93	7
Texas \| Other revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,304	61
Texas \| Total operating revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	3,702	1,358
Texas \| Other revenue, derivative \| Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	94	7
Texas \| Other Ancillary \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,200
Texas \| Home \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,542	1,032
Texas \| Business \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	572	260
East \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,726	482
Operating revenues	3,825	521
Lease revenue	0	0
East \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,543	352
East \| Energy revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	126	45
Derivative revenue	60	35
East \| Capacity revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	141	134
Derivative revenue	37	24
East \| Derivative revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	(4)	(20)
Derivative revenue	99	39
East \| Other revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	19	10
East \| Total operating revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	3,825	521
East \| Other revenue, derivative \| Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	6	0
East \| Home \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	702	329
East \| Business \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,841	23
West/Services/Other \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	597	94
Operating revenues	565	143
Lease revenue	2	5
West/Services/Other \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	505	18
West/Services/Other \| Energy revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	70	75
Derivative revenue	(4)	19
West/Services/Other \| Capacity revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	15
Derivative revenue	0	0
West/Services/Other \| Derivative revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	(28)	15
Derivative revenue	(34)	44
West/Services/Other \| Other revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	20
West/Services/Other \| Total operating revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	565	143
West/Services/Other \| Other revenue, derivative \| Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	(2)	10
West/Services/Other \| Home \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	474	18
West/Services/Other \| Business \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 31	$ 0

Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities

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- Definition

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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- Definition

Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable.

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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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- Definition

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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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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