Unconsolidated Affiliate (CenterPoint Energy and CERC) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2019		Jun. 30, 2018	Jun. 30, 2019		Jun. 30, 2018	Dec. 31, 2018
Enable Units [Abstract]
Preferred units – unconsolidated affiliate		$ 363			$ 363			$ 363
Percentage of sales that trigger right of first refusal					5.00%
Enable Distributions [Abstract]
Total distributions received from Enable		84		$ 84	$ 167		$ 167
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) [Abstract]
Equity in earnings of unconsolidated affiliate, net		74		58	136		127
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Investment in unconsolidated affiliates		2,470			2,470			2,482
CERC Corp [Member]
Enable Distributions [Abstract]
Total distributions received from Enable				75			149
Discontinued Operation, Income (Loss) from Discontinued Operation Disclosures [Abstract]
Income tax expense		0		14	0		31
Income from discontinued operations (net of tax of $-0-, $14, $-0- and $31, respectively)		0		44	$ 0		96
OGE [Member]
Enable Units [Abstract]
Percentage of sales that trigger right of first refusal					5.00%
Proliance Holdings LLC [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Investment in unconsolidated affiliates		$ 1	[1]		$ 1	[1]		0
Enable Midstream Partners [Member]
Enable Partnership Interest [Abstract]
Ownership percentage of equity method investment	[2]	53.80%			53.80%
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) [Abstract]
Operating revenues		$ 735		805	$ 1,530		1,553
Cost of sales, excluding depreciation and amortization		317		444	695		819
Depreciation and amortization		110		96	215		192
Operating income		167		126	332		265
Net income attributable to Enable common units		115		86	228		191
CenterPoint Energy’s interest		62		46	123		103
Basis difference amortization (1)	[3]	12		12	24		24
Loss on dilution, net of proportional basis difference recognition		0		0	(11)		0
Equity in earnings of unconsolidated affiliate, net		74		58	136		127
Equity Method Investment, Summarized Financial Information, Assets and Liabilities [Abstract]
Current assets		376			376			449
Non-current assets		12,033			12,033			11,995
Current liabilities		1,270			1,270			1,615
Non-current liabilities		3,580			3,580			3,211
Non-controlling interest		37			37			38
Preferred equity		362			362			362
Accumulated other comprehensive loss		(3)			(3)			0
Enable partners’ equity		7,163			7,163			7,218
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s ownership interest in Enable partners’ equity		3,850			3,850			3,896
CenterPoint Energy’s basis difference		(1,381)			(1,381)			(1,414)
Investment in unconsolidated affiliates		2,469			2,469			2,482
Enable Midstream Partners [Member] | Common Units [Member]
Enable Distributions [Abstract]
Distributions received from Enable equity method investment	[4]	$ 75		$ 75	$ 149		$ 149
Distribution per share of common units		$ 0.3180		$ 0.3180	$ 0.6360		$ 0.6360
Enable Midstream Partners [Member] | Series A Preferred Units [Member]
Enable Distributions [Abstract]
Distributions received from Enable cost method investment		$ 9		$ 9	$ 18		$ 18
Distribution per share of Series A preferred units		$ 0.6250		$ 0.6250	$ 1.2500		$ 1.2500
Enable Midstream Partners [Member] | CERC Corp [Member] | Common Units [Member]
Enable Distributions [Abstract]
Distributions received from Enable equity method investment	[4]			$ 75			$ 149
Distribution per share of common units				$ 0.3180			$ 0.6360
Common Units [Member] | Enable Midstream Partners [Member]
Enable Units [Abstract]
Limited partner interest units held	[5]	233,856,623			233,856,623
Series A Preferred Units [Member] | Enable Midstream Partners [Member]
Enable Units [Abstract]
Preferred Units Held	[6]	14,520,000			14,520,000
Transitional Service [Member] | Enable Midstream Partners [Member]
Transactions with Enable [Abstract]
Reimbursement of support services (2)	[7]	$ 1		$ 1	$ 3		$ 3
Accounts receivable for amounts billed for services provided to Enable		3			3			2
Transitional Service [Member] | Enable Midstream Partners [Member] | CERC Corp [Member]
Transactions with Enable [Abstract]
Reimbursement of support services (2)	[7]	1		1	3		3
Accounts receivable for amounts billed for services provided to Enable		3			3			2
Natural Gas Expenses [Member] | Enable Midstream Partners [Member]
Transactions with Enable [Abstract]
Natural gas expenses, including transportation and storage costs (1)	[8]	28		29	63		66
Accounts payable for natural gas purchases from Enable		9			9			11
Natural Gas Expenses [Member] | Enable Midstream Partners [Member] | CERC Corp [Member]
Transactions with Enable [Abstract]
Natural gas expenses, including transportation and storage costs (1)	[8]	28		29	63		66
Accounts payable for natural gas purchases from Enable		$ 9			$ 9			$ 11
Enable Midstream Partners [Member]
Enable Partnership Interest [Abstract]
Limited partner ownership interest	[2]				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	[2]				25.50%
Enable Midstream Partners [Member] | Public unitholders [Member]
Enable Partnership Interest [Abstract]
Limited partner ownership interest	[2]				20.70%
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	[5]	435,073,301			435,073,301
Enable Midstream Partners [Member] | Common Units [Member] | OGE [Member]
Enable Units [Abstract]
Limited partner interest units held	[5]	110,982,805			110,982,805
Enable Midstream Partners [Member] | Common Units [Member] | Public unitholders [Member]
Enable Units [Abstract]
Limited partner interest units held	[5]	90,233,873			90,233,873
Enable GP, LLC [Member] | CenterPoint Energy [Member]
Enable Units [Abstract]
Management rights ownership percentage	[9],[10]				50.00%
Incentive distribution right	[10],[11]				40.00%
Enable GP, LLC [Member] | OGE [Member]
Enable Units [Abstract]
Management rights ownership percentage	[9]				50.00%
Incentive distribution right	[11]				60.00%
Enable Midstream Partners [Member] | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | CERC Corp [Member]
Discontinued Operation, Income (Loss) from Discontinued Operation Disclosures [Abstract]
Equity in earnings of unconsolidated affiliate, net				58			127
Income tax expense				14			31
Income from discontinued operations (net of tax of $-0-, $14, $-0- and $31, respectively)				$ 44			$ 96

[1] Represents the equity investment in ProLiance Holdings, LLC related primarily to an investment in LA Storage, LLC, a joint venture in a development project for salt-cavern natural gas storage, which was acquired in the Merger. This presentation reflects preliminary fair value of the equity investment and is subject to change. See Note 3.

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

[3] 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.

[4] Prior to the Internal Spin in September 2018, distributions from Enable were received by CERC. After such date, distributions from Enable were received by CenterPoint Energy.

[5] Held indirectly through CNP Midstream by CenterPoint Energy.

[6] The carrying amount of the Enable Series A Preferred Units, reflected as Preferred units - unconsolidated affiliate on CenterPoint Energy’s Condensed Consolidated Balance Sheets, was $363 million as of June 30, 2019 and $363 million as of December 31, 2018. No impairment charges or adjustment due to observable price changes were made during the current or prior reporting periods.

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

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

[9] 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.

[10] Held indirectly through CNP Midstream.

[11] 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.