CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 147	$ 241
Investment in marketable securities	871	822
Accounts receivable	676	702
Accrued Unbilled Revenues	505	469
Natural gas and coal inventory	203	209
Materials and supplies	297	263
Taxes receivable	82	106
Current assets held for sale	0	1,002
Prepaid expense and other current assets	139	123
Total current assets	2,920	3,937
Property, Plant and Equipment, net
Property, Plant and Equipment, Gross	32,514	30,324
Accumulated Depreciation, and Amortization	10,152	9,700
Property, Plant and Equipment, Net, Total	22,362	20,624
Other Assets:
Goodwill	4,697	4,882
Regulatory assets	2,094	2,117
Investment in unconsolidated affiliates	783	2,408
Preferred units - unconsolidated affiliate	363	363
Non-current assets held for sale	0	962
Other	252	236
Total other assets	8,189	10,968
Total Assets	33,471	35,529
Current Liabilities:
Short-term borrowings	24	0
Current portion of VIE Securitization Bonds long-term debt	211	231
Indexed debt, net	15	19
Current portion of other long-term debt	1,669	618
Indexed debt securities derivative	953	893
Accounts payable	853	884
Taxes accrued	265	239
Interest accrued	145	158
Dividends accrued	136	0
Customer deposits	119	124
Non-trading derivative liabilities	3	7
Current liabilities held for sale	0	455
Other	432	350
Total current liabilities	4,825	3,978
Other Liabilities:
Deferred income taxes, net	3,603	3,928
Non-trading derivative liabilities	27	15
Benefit obligations	680	750
Regulatory liabilities	3,448	3,474
Non-current liabilities held for sale	0	43
Other	1,019	738
Total other liabilities	8,777	8,948
Long-term Debt:
VIE Securitization Bonds, net	536	746
Other long-term debt, net	10,985	13,498
Total long-term debt, net	11,521	14,244
Commitments and Contingencies
Shareholders’ Equity:
Common stock	6	5
Additional paid-in capital	6,914	6,080
Retained earnings (accumulated deficit)	(845)	632
Accumulated other comprehensive income (loss)	(90)	(98)
Total shareholders’ equity	8,348	8,359
Total Liabilities and Shareholders’ Equity	33,471	35,529
Supplemental Income Statement Elements [Abstract]
Bad debt reserve	52	21
Accrued Unbilled Revenues, Allowance for Credit Losses, Current	5	0
Cumulative preferred stock, $0.01 par value, 20,000,000 shares authorized
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common stock, $0.01 par value	$ 0.01	$ 0.01
Common Stock, Shares, Outstanding	551,355,861	502,242,061
Variable Interest Entity, Primary Beneficiary [Member]
Current Assets:
Cash and cash equivalents	$ 139	$ 216
Accounts receivable	23	26
Prepaid expense and other current assets	15	19
Other Assets:
Regulatory assets	633	788
Houston Electric [Member]
Current Assets:
Cash and cash equivalents	139	216
Accounts and notes receivable, net	268	238
Accounts and notes receivable—affiliated companies	7	523
Accrued Unbilled Revenues	113	117
Materials and supplies	195	147
Prepaid expense and other current assets	47	49
Total current assets	769	1,290
Property, Plant and Equipment, net
Property, Plant and Equipment, Gross	13,593	12,829
Accumulated Depreciation, and Amortization	3,930	3,797
Property, Plant and Equipment, Net, Total	9,663	9,032
Other Assets:
Regulatory assets	848	915
Other	36	25
Total other assets	884	940
Total Assets	11,316	11,262
Current Liabilities:
Current portion of VIE Securitization Bonds long-term debt	211	231
Current portion of other long-term debt	402	0
Accounts payable	281	268
Accounts payable - affiliated companies	96	76
Taxes accrued	158	123
Interest accrued	71	69
Other	117	63
Total current liabilities	1,336	830
Other Liabilities:
Deferred income taxes, net	1,041	1,030
Benefit obligations	75	75
Regulatory liabilities	1,252	1,288
Other	95	69
Total other liabilities	2,463	2,462
Long-term Debt:
VIE Securitization Bonds, net	536	746
Other long-term debt, net	3,870	3,973
Total long-term debt, net	4,406	4,719
Commitments and Contingencies
Shareholders’ Equity:
Common stock	0	0
Additional paid-in capital	2,548	2,486
Retained earnings (accumulated deficit)	563	780
Accumulated other comprehensive income (loss)	0	(15)
Total shareholders’ equity	3,111	3,251
Total Liabilities and Shareholders’ Equity	11,316	11,262
Supplemental Income Statement Elements [Abstract]
Bad debt reserve	1	1
Houston Electric [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Current Assets:
Cash and cash equivalents	139	216
Accounts receivable	23	26
Prepaid expense and other current assets	15	19
Other Assets:
Regulatory assets	633	788
CERC Corp [Member]
Current Assets:
Cash and cash equivalents	1	2
Accounts receivable	233	322
Accounts and notes receivable—affiliated companies	8	10
Accrued Unbilled Revenues	260	249
Natural gas and coal inventory	121	135
Materials and supplies	58	71
Current assets held for sale	0	691
Prepaid expense and other current assets	26	9
Total current assets	707	1,489
Property, Plant and Equipment, net
Property, Plant and Equipment, Gross	8,972	8,079
Accumulated Depreciation, and Amortization	2,414	2,270
Property, Plant and Equipment, Net, Total	6,558	5,809
Other Assets:
Goodwill	757	757
Regulatory assets	220	191
Non-current assets held for sale	0	213
Other	66	53
Total other assets	1,043	1,214
Total Assets	8,308	8,512
Current Liabilities:
Short-term borrowings	24	0
Accounts payable	296	333
Accounts payable - affiliated companies	50	47
Taxes accrued	74	84
Interest accrued	28	38
Customer deposits	76	74
Current liabilities held for sale	0	368
Other	178	167
Total current liabilities	726	1,111
Other Liabilities:
Deferred income taxes, net	584	470
Benefit obligations	83	80
Regulatory liabilities	1,226	1,219
Non-current liabilities held for sale	0	27
Other	694	418
Total other liabilities	2,587	2,214
Long-term Debt:
Total long-term debt, net	2,428	2,546
Commitments and Contingencies
Shareholders’ Equity:
Common stock	0	0
Additional paid-in capital	2,046	2,116
Retained earnings (accumulated deficit)	511	515
Accumulated other comprehensive income (loss)	10	10
Total shareholders’ equity	2,567	2,641
Total Liabilities and Shareholders’ Equity	8,308	8,512
Supplemental Income Statement Elements [Abstract]
Bad debt reserve	45	15
Accrued Unbilled Revenues, Allowance for Credit Losses, Current	4	0
Series A Preferred Stock [Member]
Shareholders’ Equity:
Preferred Stock	$ 790	$ 790
Supplemental Income Statement Elements [Abstract]
Preferred Stock, $0.01 par value	$ 0.01	$ 0.01
Preferred stock aggregate liquidation preference	$ 800	$ 800
Preferred stock outstanding (in shares)	800,000	800,000
Series B Preferred Stock [Member]
Shareholders’ Equity:
Preferred Stock	$ 950	$ 950
Supplemental Income Statement Elements [Abstract]
Preferred Stock, $0.01 par value	$ 0.01	$ 0.01
Preferred stock aggregate liquidation preference	$ 977	$ 977
Preferred stock outstanding (in shares)	977,400	977,400
Series C Preferred Stock [Member]
Shareholders’ Equity:
Preferred Stock	$ 623	$ 0
Supplemental Income Statement Elements [Abstract]
Preferred Stock, $0.01 par value	$ 0.01	$ 0.01
Preferred stock aggregate liquidation preference	$ 625
Preferred stock outstanding (in shares)	625,000
Cumulative Preferred Stock [Member]
Supplemental Income Statement Elements [Abstract]
Preferred Stock, $0.01 par value	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	20,000,000	20,000,000