Unconsolidated Affiliate (CenterPoint Energy and CERC) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares	Feb. 18, 2021	Dec. 31, 2017 USD ($)
Enable Units [Abstract]
Preferred units - unconsolidated affiliate	$ 363	$ 363
Percentage of sales that trigger right of first refusal	5.00%
Enable Distributions [Abstract]
Distributions from unconsolidated affiliates	$ 113	261	$ 267
Total distributions received from Enable	229	339	333
Income Statement [Abstract]
Operating revenues	7,418	7,564	6,277
Goodwill impairment	185	0	0
Net income (loss) attributable to Enable common units	(949)	674	333
CenterPoint Energy’s equity in earnings (losses), net	(1,428)	230	307
ASSETS
Current assets	2,920	3,937
LIABILITIES AND SHAREHOLDERS’ EQUITY
Current liabilities	4,825	3,978
Enable partners' equity	8,348	8,359	8,058
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s equity method investment in Enable	$ 783	2,408
Enable Series A Distribution Rate	0.10
Subsequent Event [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Enable Series A Distribution Rate				0.085
Common Units [Member]
LIABILITIES AND SHAREHOLDERS’ EQUITY
Enable partners' equity	$ 6	5	5		$ 4
Series A Preferred Units [Member]
LIABILITIES AND SHAREHOLDERS’ EQUITY
Enable partners' equity	2,363	1,740	1,740		0
CERC Corp [Member]
Enable Distributions [Abstract]
Distributions from unconsolidated affiliates	0	0	176
Transaction with Enable [Abstract]
Natural gas expenses, including transportation and storage costs (1)	23
Income Statement [Abstract]
Operating revenues	2,763	3,018	3,031
CenterPoint Energy’s equity in earnings (losses), net	0	0	184
ASSETS
Current assets	707	1,489
LIABILITIES AND SHAREHOLDERS’ EQUITY
Current liabilities	726	1,111
Enable partners' equity	2,567	2,641	2,443
CERC Corp [Member] | Common Units [Member]
LIABILITIES AND SHAREHOLDERS’ EQUITY
Enable partners' equity	0	0	0		$ 0
CenterPoint Energy [Member]
Income Statement [Abstract]
Operating revenues	$ 7,418	7,564	6,277
Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Share Price | $ / shares	$ 5.26
OGE [Member]
Enable Units [Abstract]
Percentage of sales that trigger right of first refusal	5.00%
Non-utility Investments [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s equity method investment in Enable	$ 1
Proliance Holdings LLC [Member]
Income Statement [Abstract]
CenterPoint Energy’s equity in earnings (losses), net	$ 0	1	0
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s equity method investment in Enable		$ 2
Enable Midstream Partners [Member]
Enable Partnership Interest [Abstract]
Limited partner ownership interest	53.70%	53.70%
Limited partner ownership interest	100.00%	100.00%
Enable Units [Abstract]
Maximum incentive distribution right	50.00%
Income Statement [Abstract]
Operating revenues	$ 2,463	$ 2,960	3,431
Cost of sales, excluding depreciation and amortization	965	1,279	1,819
Depreciation and amortization	420	433	398
Operating income	465	569	648
Goodwill impairment	28	86	0
Net income (loss) attributable to Enable common units	52	360	485
CenterPoint Energy’s interest	28	193	262
Basis difference amortization (1)	87	47	47
Loss on dilution, net of proportional basis difference recognition	(2)	(11)	(2)
Impairment of CenterPoint Energy’s equity method investment in Enable	(1,541)	0	0
Equity Method Investment's Impairment on an equity method investment	225
CenterPoint Energy’s equity in earnings (losses), net	(1,428)	229	$ 307
ASSETS
Current assets	381	389
Non-current assets	11,348	11,877
LIABILITIES AND SHAREHOLDERS’ EQUITY
Current liabilities	582	780
Non-current liabilities	4,052	4,077
Non-controlling interest	26	37
Preferred equity	362	362
Accumulated other comprehensive loss	(6)	(3)
Enable partners' equity	6,713	7,013
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s ownership interest in Enable partners’ equity	3,601	3,767
CenterPoint Energy’s basis difference (1)	(2,819)	(1,361)
CenterPoint Energy’s equity method investment in Enable	$ 782	$ 2,406
Equity Method Investment Carrying Value Per Unit | $ / shares	$ 3.34
Enable Midstream Partners [Member] | Common Units [Member]
Enable Distributions [Abstract]
Distribution per share of common units | $ / shares	$ 0.8263	$ 1.2970	$ 1.2720
Distributions from unconsolidated affiliates	$ 193	$ 303	$ 297
Enable Midstream Partners [Member] | Series A Preferred Units [Member]
Enable Distributions [Abstract]
Distribution per share of Series A preferred units | $ / shares	$ 2.5000	$ 2.5000	$ 2.5000
Distributions received from Enable cost method investment	$ 36	$ 36	$ 36
Enable Midstream Partners [Member] | OGE [Member]
Enable Partnership Interest [Abstract]
Limited partner ownership interest	25.50%	25.50%
Enable Midstream Partners [Member] | Public unitholders [Member]
Enable Partnership Interest [Abstract]
Limited partner ownership interest	20.80%	20.80%
Maximum [Member] | Enable Midstream Partners [Member]
Enable Units [Abstract]
Incentive distribution per unit | $ / shares	$ 0.330625
Common Units [Member] | Enable Midstream Partners [Member]
Enable Units [Abstract]
Limited partner interest units held | shares	233,856,623	233,856,623
Limited partner interest units held | shares	435,549,892	435,201,365
Common Units [Member] | Enable Midstream Partners [Member] | OGE [Member]
Enable Units [Abstract]
Limited partner interest units held | shares	110,982,805	110,982,805
Common Units [Member] | Enable Midstream Partners [Member] | Public unitholders [Member]
Enable Units [Abstract]
Limited partner interest units held | shares	90,710,464	90,361,937
Series A Preferred Units [Member] | Enable Midstream Partners [Member]
Enable Units [Abstract]
Preferred units held | shares	14,520,000	14,520,000
Series A Preferred Units [Member] | Enable Midstream Partners [Member] | OGE [Member]
Enable Units [Abstract]
Preferred units held | shares	0	0
Series A Preferred Units [Member] | Enable Midstream Partners [Member] | Public unitholders [Member]
Enable Units [Abstract]
Preferred units held | shares	0	0
Enable Midstream Partners [Member] | CERC Corp [Member]
Transaction with Enable [Abstract]
Accounts Receivable, Related Parties	$ 1	$ 2
Natural Gas Expenses [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Natural gas expenses, including transportation and storage costs (1)	86	86	86
Accounts payable for natural gas purchases from Enable	9	9
Natural Gas Expenses [Member] | Enable Midstream Partners [Member] | CERC Corp [Member]
Transaction with Enable [Abstract]
Natural gas expenses, including transportation and storage costs (1)	86	86	86
Accounts payable for natural gas purchases from Enable	9	9
Transitional Service [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Related Party Transaction, Other Revenues from Transactions with Related Party	0	0	4
Accounts Receivable, Related Parties	1	2
Transitional Service [Member] | Enable Midstream Partners [Member] | CERC Corp [Member]
Transaction with Enable [Abstract]
Related Party Transaction, Other Revenues from Transactions with Related Party	$ 0	$ 0	$ 4
Enable GP, LLC [Member]
Enable Units [Abstract]
Management rights ownership percentage	50.00%
Incentive distribution right	40.00%
Enable GP, LLC [Member] | CenterPoint Energy [Member]
Enable Units [Abstract]
Management rights ownership percentage	50.00%
Incentive distribution right	40.00%
Enable GP, LLC [Member] | OGE [Member]
Enable Units [Abstract]
Management rights ownership percentage	50.00%
Incentive distribution right	60.00%