Unconsolidated Affiliate (CenterPoint Energy and CERC) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018		Sep. 30, 2018	[1]	Jun. 30, 2018	[1]	Mar. 31, 2018	[1]	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Enable Units [Abstract]
Preferred units - unconsolidated affiliate		$ 363								$ 363		$ 363
Percentage of sales that trigger right of first refusal										5.00%
Enable Distributions [Abstract]
Proceeds from Equity Method Investment, Distribution										$ 261		267	$ 0
Total distributions received from Enable										339		333	333
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Goodwill impairment										48		0	0
CenterPoint Energy’s equity in earnings, net										230		307	265
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s equity method investment in Enable		2,482								2,408		2,482
CERC Corp [Member]
Contribution from parent										129		960	38
Enable Distributions [Abstract]
Total distributions received from Enable												223	297
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Goodwill impairment										48		0	0
Discontinued Operation, Income (Loss) from Discontinued Operation Disclosures [Abstract]
Income tax expense										0		46	104
Income (loss) from discontinued operations, net of tax		(2)	[1]	$ 44		$ 44		$ 52		$ 0		138	161
Enable Midstream Partners [Member]
Share Price										$ 10.03
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	[2]									$ 2
Proliance Holdings LLC [Member]
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
CenterPoint Energy’s equity in earnings, net										1		0	0
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s equity method investment in Enable		$ 0										$ 0
Enable Midstream Partners [Member]
Equity Method Investment Decrease in Carrying Value										$ 61
Equity Method Investment Carrying Value Per Unit										$ 10.29
Enable Partnership Interest [Abstract]
Limited partner ownership interest	[3],[4]	54.00%								53.70%		54.00%
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Operating revenues										$ 2,960		$ 3,431	2,803
Cost of sales, excluding depreciation and amortization										1,279		1,819	1,381
Depreciation and amortization										433		398	366
Operating income										569		648	528
Goodwill impairment										86
Net income attributable to Enable common units										360		485	400
CenterPoint Energy’s interest										193		262	216
Basis difference amortization (1)	[5]									47		47	49
Loss on dilution, net of proportional basis difference recognition										(11)		(2)	0
CenterPoint Energy’s equity in earnings, net	[6],[7]									229		307	$ 265
Equity Method Investment, Summarized Financial Information [Abstract]
Current assets		$ 449								389		449
Non-current assets		11,995								11,877		11,995
Current liabilities		1,615								780		1,615
Non-current liabilities		3,211								4,077		3,211
Non-controlling interest		38								37		38
Preferred equity		362								362		362
Equity Method Investment Summarized Financial Information Accumulated Other Comprehensive Income Loss										(3)
Enable partners’ equity		7,218								7,013		7,218
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s ownership interest in Enable partners’ equity		3,896								3,767		3,896
CenterPoint Energy’s basis difference		(1,414)								(1,361)		(1,414)
CenterPoint Energy’s equity method investment in Enable		$ 2,482								$ 2,406		$ 2,482
Enable Midstream Partners [Member] | Common Units [Member]
Enable Distributions [Abstract]
Distribution per share of common units										$ 1.2970		$ 1.2720	$ 1.2720
Proceeds from Equity Method Investment, Distribution										$ 303	[8]	$ 297	$ 297
Enable Midstream Partners [Member] | Series A Preferred Units [Member]
Enable Distributions [Abstract]
Distribution per share of Series A preferred units										$ 2.5000		$ 2.5000	$ 2.5000
Distributions received from Enable cost method investment										$ 36		$ 36	$ 36
Enable Midstream Partners [Member] | CERC Corp [Member] | Common Units [Member]
Enable Distributions [Abstract]
Distribution per share of common units	[8]											$ 0.9540	$ 1.2720
Proceeds from Equity Method Investment, Distribution	[8]											$ 223	$ 297
Common Units [Member] | Enable Midstream Partners [Member]
Enable Units [Abstract]
Limited partner interest units held	[4]	233,856,623								233,856,623		233,856,623
Series A Preferred Units [Member] | Enable Midstream Partners [Member]
Enable Units [Abstract]
Preferred units held	[4],[9]	14,520,000								14,520,000		14,520,000
Natural Gas Expenses [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Natural gas expenses, including transportation and storage costs (1)	[10]									$ 120		$ 122	115
Accounts payable for natural gas purchases from Enable		$ 11								11		11
Natural Gas Expenses [Member] | Enable Midstream Partners [Member] | CERC Corp [Member]
Transaction with Enable [Abstract]
Natural gas expenses, including transportation and storage costs (1)	[10]									120		122	115
Accounts payable for natural gas purchases from Enable		11								11		11
Transitional Service [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Reimbursement of support services (2)	[7]									0		4	4
Accounts receivable for amounts billed for services provided to Enable		2								2		2
Transitional Service [Member] | Enable Midstream Partners [Member] | CERC Corp [Member]
Transaction with Enable [Abstract]
Reimbursement of support services (2)	[7]									0		4	4
Accounts receivable for amounts billed for services provided to Enable		$ 2								$ 2		$ 2
Enable Midstream Partners [Member]
Enable Partnership Interest [Abstract]
Limited partner ownership interest	[3]									100.00%		100.00%
Enable Units [Abstract]
Maximum incentive distribution right										50.00%
Enable Midstream Partners [Member] | OGE [Member]
Enable Partnership Interest [Abstract]
Limited partner ownership interest	[3]									25.50%		25.60%
Enable Midstream Partners [Member] | Public unitholders [Member]
Enable Partnership Interest [Abstract]
Limited partner ownership interest	[3]									20.80%		20.40%
Enable Midstream Partners [Member] | Minimum [Member]
Enable Units [Abstract]
Incentive distribution per unit										$ 0.2875
Enable Midstream Partners [Member] | Maximum [Member]
Enable Units [Abstract]
Incentive distribution per unit										$ 0.330625
Enable Midstream Partners [Member] | Common Units [Member]
Enable Units [Abstract]
Limited partner interest units held		433,232,411								435,201,365		433,232,411
Enable Midstream Partners [Member] | Common Units [Member] | OGE [Member]
Enable Units [Abstract]
Limited partner interest units held		110,982,805								110,982,805		110,982,805
Enable Midstream Partners [Member] | Common Units [Member] | Public unitholders [Member]
Enable Units [Abstract]
Limited partner interest units held		88,392,983								90,361,937		88,392,983
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Enable Midstream Partners [Member] | CERC Corp [Member]
Investment in unconsolidated affiliates - discontinued operations	[11]												2,472
Discontinued Operation, Income (Loss) from Discontinued Operation Disclosures [Abstract]
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax												$ 184	265
Income tax expense												46	104
Income (loss) from discontinued operations, net of tax												$ 138	$ 161
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	[12],[13]									50.00%
Incentive distribution right	[13],[14]									40.00%
Enable GP, LLC [Member] | OGE [Member]
Enable Units [Abstract]
Management rights ownership percentage	[12]									50.00%
Incentive distribution right	[14]									60.00%

[1] Amounts have been recast to reflect discontinued operations in all periods presented.

[2] Represents the fair value of non-utility equity investments acquired in the Merger.

[3] Excludes the Enable Series A Preferred Units owned by CenterPoint Energy.

[4] Prior to the Internal Spin completed in September 2018, CenterPoint Energy’s investment in Enable’s common units, excluding the Enable Series A Preferred Units held directly by CenterPoint Energy, was held indirectly through CERC.

[5] Equity in earnings of unconsolidated affiliate includes CenterPoint Energy’s share of Enable earnings adjusted for the amortization of the basis difference of CenterPoint Energy’s original investment in Enable and its underlying equity in net assets of Enable. The basis difference is being amortized through the year 2048.

[6] Equity earnings for the year ended December 31, 2019 includes CenterPoint Energy’s share of Enable’s $86 million goodwill impairment recorded in the fourth quarter of 2019.

[7] Represents amounts billed for certain support services provided to Enable. Actual support services costs are recorded net of reimbursement.

[8] Prior to the Internal Spin completed in September 2018, distributions from Enable were received by CERC. After such date, distributions from Enable were received directly by CenterPoint Energy (through CNP Midstream).

[9] The carrying amount of the Enable Series A Preferred Units, reflected as Preferred units - unconsolidated affiliate on CenterPoint Energy’s Consolidated Balance Sheets, was $363 million as of both December 31, 2019 and 2018. No impairment charges or adjustment to carrying value were made as no observable price changes were identified in the current or prior reporting periods.

[10] Included in Non-utility costs of revenues, including natural gas on CenterPoint Energy’s and CERC’s respective Statements of Consolidated Income.

[11] On September 4, 2018, CERC completed the Internal Spin. For further information regarding the Internal Spin, see Note 11.

[12] As of December 31, 2019, Enable is controlled jointly by CenterPoint Energy and OGE. Sale of CenterPoint Energy’s or OGE’s ownership interests in Enable GP to a third party is subject to mutual rights of first offer and first refusal, and CenterPoint Energy is not permitted to dispose of less than all of its interest in Enable GP.

[13] Held indirectly through CNP Midstream.

[14] Enable is expected to pay a minimum quarterly distribution of $0.2875 per common unit on its outstanding common units to the extent it has sufficient cash from operations after establishment of cash reserves and payment of fees and expenses, including payments to Enable GP and its affiliates, within 60 days after the end of each quarter. If cash distributions to Enable’s unitholders exceed $0.330625 per common unit in any quarter, Enable GP will receive increasing percentages or incentive distributions rights, up to 50%, of the cash Enable distributes in excess of that amount. In certain circumstances Enable GP will have the right to reset the minimum quarterly distribution and the target distribution levels at which the incentive distributions receive increasing percentages to higher levels based on Enable’s cash distributions at the time of the exercise of this reset election. To date, no incentive distributions have been made.