Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 6,490	$ 2,684	$ 19,687	$ 6,733
Mark-to-market for economic hedging activities	1,785	(118)	4,023	13
Operating revenues	6,609	2,809	19,943	7,066
Lease revenue	2	5	6	15
Derivative revenue	1,793	(123)	4,025	18
Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(1)	(3)	(5)	(6)
Operating revenues	13	2	15	(1)
Lease revenue	0	0	0	0
Retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,951	2,302	16,929	5,795
Retail revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	(1)	(1)
Energy revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	336	222	989	429
Derivative revenue	41	35	120	99
Energy revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	1	6	(1)
Derivative revenue	1	(1)	2	(3)
Capacity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	189	174	615	518
Derivative revenue	42	49	119	114
Capacity revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Derivative revenue	0	0	0	0
Derivative revenue
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	3	39	(99)	78
Derivative revenue	120	120	269	318
Derivative revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	13	5	19	8
Derivative revenue	14	5	20	5
Other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	133	72	1,528	246
Contract amortization	(3)		(19)
Other revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(4)	(4)	(9)	(7)
Contract amortization	0		0
Total operating revenue
Disaggregation of Revenue [Line Items]
Operating revenues	6,609	2,809	19,943	7,066
Total operating revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	13	2	15	(1)
Other revenue, derivative
Disaggregation of Revenue [Line Items]
Derivative revenue	34	(3)	129	27
Other revenue, derivative \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Derivative revenue	0	1	(1)	0
Home \| Retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,646	1,987	7,391	4,929
Home \| Retail revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	(1)	(1)
Business \| Retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,305	315	9,538	866
Business \| Retail revenue \| Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Texas \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,597	1,982	8,233	4,904
Operating revenues	2,635	1,992	8,362	4,928
Lease revenue	0	0	0	0
Texas \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,503	1,921	6,575	4,734
Texas \| Energy revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18	11	317	21
Derivative revenue	0	0	0	0
Texas \| Capacity revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Derivative revenue	0	0	0	0
Texas \| Derivative revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	(1)	1	(5)	1
Derivative revenue	38	10	129	24
Texas \| Other revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	115	59	1,475	172
Contract amortization	0		0
Texas \| Total operating revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	2,635	1,992	8,362	4,928
Texas \| Other revenue, derivative \| Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	39	9	134	23
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	1,776	1,633	4,484	3,938
Texas \| Business \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	727	288	2,091	796
East \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,008	551	8,823	1,492
Operating revenues	3,077	666	9,002	1,732
Lease revenue	0	0	1	1
East \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,698	354	8,029	996
East \| Energy revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	201	93	428	157
Derivative revenue	38	23	122	60
East \| Capacity revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	172	158	568	471
Derivative revenue	42	49	119	114
East \| Derivative revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	(3)	43	(53)	63
Derivative revenue	76	115	193	239
East \| Other revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	16	18	45	45
Contract amortization	(7)		(15)
East \| Total operating revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	3,077	666	9,002	1,732
East \| Other revenue, derivative \| Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	(1)	0	5	2
East \| Home \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	470	327	1,469	926
East \| Business \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,228	27	6,560	70
West/Services/Other \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	886	154	2,636	343
Operating revenues	884	149	2,564	407
Lease revenue	2	5	5	14
West/Services/Other \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	750	27	2,326	66
West/Services/Other \| Energy revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	113	117	238	252
Derivative revenue	2	13	(4)	42
West/Services/Other \| Capacity revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	17	16	47	47
Derivative revenue	0	0	0	0
West/Services/Other \| Derivative revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	(6)	(10)	(60)	6
Derivative revenue	(8)	(10)	(73)	50
West/Services/Other \| Other revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	(1)	17	36
Contract amortization	4		(4)
West/Services/Other \| Total operating revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	884	149	2,564	407
West/Services/Other \| Other revenue, derivative \| Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	(4)	(13)	(9)	2
West/Services/Other \| Home \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	400	27	1,439	66
West/Services/Other \| Business \| Retail revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 350	$ 0	$ 887	$ 0

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

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- Definition

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

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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 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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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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