STATEMENTS OF CONSOLIDATED INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Utility revenues	$ 7,049	$ 7,202	$ 6,199
Non-utility revenues	369	362	78
Total	7,418	7,564	6,277
Expenses:
Utility natural gas, fuel and purchased power	1,488	1,762	1,464
Non-utility cost of revenues, including natural gas	257	257	40
Operation and maintenance	2,744	2,775	2,271
Depreciation and amortization	1,189	1,225	1,230
Taxes other than income taxes	516	474	404
Goodwill impairment	185	0	0
Total	6,379	6,493	5,409
Operating Income	1,039	1,071	868
Other Income (Expense):
Gain (loss) on marketable securities	49	282	(22)
Loss on indexed debt securities	(60)	(292)	(232)
Interest expense and other finance charges	(501)	(528)	(361)
Interest expense on Securitization Bonds	(28)	(39)	(59)
Equity in earnings (loss) of unconsolidated affiliates, net	(1,428)	230	307
Interest Income	3	17	24
Interest Income on Securitization Bonds	1	5	4
Other income, net	60	28	22
Total	(1,904)	(297)	(317)
Income (Loss) from Continuing Operations Before Income Taxes	(865)	774	551
Income tax expense (benefit)	(274)	92	155
Income From Continuing Operations	(591)	682	396
Income (Loss) from Discontinued Operations	(182)	109	(28)
Net Income (Loss)	(773)	791	368
Income allocated to preferred shareholders	176	117	35
Income (Loss) Available to Common Shareholders	(949)	674	333
Supplemental Income Statement Elements [Abstract]
Income tax expense (benefit) from discontinued operations	$ 21	$ 46	$ (9)
Earnings Per Share, Basic [Abstract]
Basic earnings (loss) per common share - continuing operations	$ (1.45)	$ 1.12	$ 0.80
Basic earnings (loss) per common share - discontinued operations	(0.34)	0.22	(0.06)
Earnings Per Share, Basic	(1.79)	1.34	0.74
Earnings Per Share, Diluted [Abstract]
Diluted earnings (loss) per common share - continuing operations	(1.45)	1.12	0.80
Diluted earnings (loss) per common share - discontinued operations	(0.34)	0.21	(0.06)
Diluted Earnings (Loss) Per Common Share	$ (1.79)	$ 1.33	$ 0.74
Weighted Average Common Shares Outstanding, Basic	531,031,000	502,050,000	448,829,000
Weighted Average Common Shares Outstanding, Diluted	531,031,000	505,157,000	452,465,000
Houston Electric [Member]
Revenues:
Total	$ 2,911	$ 2,990	$ 3,234
Expenses:
Operation and maintenance	1,523	1,477	1,452
Depreciation and amortization	560	648	917
Taxes other than income taxes	252	247	240
Total	2,335	2,372	2,609
Operating Income	576	618	625
Other Income (Expense):
Interest expense and other finance charges	(171)	(164)	(138)
Interest expense on Securitization Bonds	(28)	(39)	(59)
Interest Income	2	22	1
Interest Income on Securitization Bonds	1	5	4
Other income, net	7	(6)	(8)
Total	(189)	(182)	(200)
Income (Loss) from Continuing Operations Before Income Taxes	387	436	425
Income tax expense (benefit)	53	80	89
Net Income (Loss)	334	356	336
CERC Corp [Member]
Revenues:
Utility revenues	2,711	2,951	2,967
Non-utility revenues	52	67	64
Total	2,763	3,018	3,031
Expenses:
Utility natural gas, fuel and purchased power	1,100	1,391	1,464
Non-utility cost of revenues, including natural gas	17	39	40
Operation and maintenance	798	824	833
Depreciation and amortization	304	293	280
Taxes other than income taxes	182	161	155
Total	2,401	2,708	2,772
Operating Income	362	310	259
Other Income (Expense):
Interest expense and other finance charges	(111)	(116)	(122)
Equity in earnings (loss) of unconsolidated affiliates, net	0	0	184
Interest Income	0	5	1
Other income, net	(7)	(13)	(9)
Total	(118)	(124)	(130)
Income (Loss) from Continuing Operations Before Income Taxes	244	186	129
Income tax expense (benefit)	97	(3)	31
Income From Continuing Operations	147	189	98
Income (Loss) from Discontinued Operations	(66)	23	110
Net Income (Loss)	81	212	208
Supplemental Income Statement Elements [Abstract]
Income tax expense (benefit) from discontinued operations	$ (2)	$ 17	$ 37