Regulatory Accounting (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Securitized regulatory assets		$ 1,146		$ 1,146		$ 1,590
Unrecognized equity return (2)	[1]	(225)		(225)		(287)
Unamortized loss on reacquired debt		70		70		75
Regulatory assets		1,934		1,934		2,347
Total regulatory assets		1,994		1,994		2,477
Regulatory liabilities		2,506		2,506		2,464
Total regulatory liabilities		2,553		2,553		2,488
Total regulatory assets and liabilities, net		(559)		(559)		(11)
Houston Electric [Member]
Securitized regulatory assets		1,146		1,146		1,590
Unrecognized equity return (2)	[1]	(225)		(225)		(287)
Unamortized loss on reacquired debt		70		70		75
Regulatory assets		1,202		1,202		1,570
Total regulatory assets		1,202		1,202		1,570
Regulatory liabilities		1,265		1,265		1,263
Total regulatory liabilities		1,287		1,287		1,285
Total regulatory assets and liabilities, net		(85)		(85)		285
Amount of allowed equity return on the true-up balance that was recognized in the period		17	$ 13	62	$ 30
CERC Corp [Member]
Securitized regulatory assets		0		0		0
Unrecognized equity return (2)	[1]	0		0		0
Unamortized loss on reacquired debt		0		0		0
Regulatory assets		170		170		181
Total regulatory assets		230		230		311
Regulatory liabilities		1,241		1,241		1,201
Total regulatory liabilities		1,266		1,266		1,203
Total regulatory assets and liabilities, net		(1,036)		(1,036)		(892)
Hurricane Harvey [Member]
Regulatory assets	[2]	67		67		64
Hurricane Harvey [Member] | Houston Electric [Member]
Regulatory assets	[2]	61		61		58
Hurricane Harvey [Member] | CERC Corp [Member]
Regulatory assets	[2]	6		6		6
Prepaid expenses and other current assets [Member]
Current regulatory assets (1)	[3]	60		60		130
Prepaid expenses and other current assets [Member] | Houston Electric [Member]
Current regulatory assets (1)	[3]	0		0		0
Prepaid expenses and other current assets [Member] | CERC Corp [Member]
Current regulatory assets (1)	[3]	60		60		130
Other current liabilities [Member]
Current regulatory liabilities (7)	[4]	47		47		24
Other current liabilities [Member] | Houston Electric [Member]
Current regulatory liabilities (7)	[4]	22		22		22
Other current liabilities [Member] | CERC Corp [Member]
Current regulatory liabilities (7)	[4]	25		25		2
Pension and Other Postretirement Plans Costs [Member]
Regulatory assets	[5]	609		609		646
Pension and Other Postretirement Plans Costs [Member] | Houston Electric [Member]
Regulatory assets	[5]	32		32		31
Pension and Other Postretirement Plans Costs [Member] | CERC Corp [Member]
Regulatory assets	[5]	15		15		20
Amounts related to TCJA [Member]
Regulatory assets	[6]	48		48		48
Amounts related to TCJA [Member] | Houston Electric [Member]
Regulatory assets	[6]	34		34		33
Amounts related to TCJA [Member] | CERC Corp [Member]
Regulatory assets	[6]	14		14		15
Other Regulatory Assets (Liabilities) [Member]
Regulatory assets	[7]	219		219		211
Other Regulatory Assets (Liabilities) [Member] | Houston Electric [Member]
Regulatory assets	[7]	84		84		70
Other Regulatory Assets (Liabilities) [Member] | CERC Corp [Member]
Regulatory assets	[7]	135		135		140
Amounts related to TCJA [Member]
Regulatory liabilities	[6]	1,362		1,362		1,354
Amounts related to TCJA [Member] | Houston Electric [Member]
Regulatory liabilities	[6]	858		858		862
Amounts related to TCJA [Member] | CERC Corp [Member]
Regulatory liabilities	[6]	504		504		492
Removal Costs [Member]
Regulatory liabilities		887		887		878
Removal Costs [Member] | Houston Electric [Member]
Regulatory liabilities		275		275		285
Removal Costs [Member] | CERC Corp [Member]
Regulatory liabilities		612		612		593
Other Regulatory Assets (Liabilities) [Member]
Regulatory liabilities		257		257		232
Other Regulatory Assets (Liabilities) [Member] | Houston Electric [Member]
Regulatory liabilities		132		132		116
Other Regulatory Assets (Liabilities) [Member] | CERC Corp [Member]
Regulatory liabilities		125		125		116
Natural Gas Distribution [Member] | Pension and Other Postretirement Plans Costs [Member]
Remaining amounts of regulatory assets for which no return on investment during recovery period is provided		$ 4		$ 4		$ 7

[1] The unrecognized equity return will be recognized as it is recovered in rates through 2024. During the three months ended September 30, 2018 and 2017, CenterPoint Energy and Houston Electric recognized approximately $17 million and $13 million, respectively, of the allowed equity return. During the nine months ended September 30, 2018 and 2017, CenterPoint Energy and Houston Electric recognized approximately $62 million and $30 million, respectively, of the allowed equity return. The timing of CenterPoint Energy’s and Houston Electric’s recognition of the equity return will vary each period based on amounts actually collected during the period. The actual amounts recognized are adjusted at least annually to correct any over-collections or under-collections during the preceding 12 months.

[2] The Registrants are not earning a return on Hurricane Harvey restoration costs.

[3] Current regulatory assets are included in Prepaid expenses and other current assets in the Registrants’ Condensed Consolidated Balance Sheets.

[4] Current regulatory liabilities are included in Other current liabilities in each of the Registrants’ respective Condensed Consolidated Balance Sheets.

[5] Includes a portion of NGD’s actuarially determined pension and other postemployment expense in excess of the amount being recovered through rates that is being deferred for rate making purposes, of which $4 million and $7 million as of September 30, 2018 and December 31, 2017, respectively, were not earning a return.

[6] The EDIT and deferred revenues will be recovered or refunded to customers as required by tax and regulatory authorities.

[7] Other long-term regulatory assets that are not earning a return were not material as of September 30, 2018 and December 31, 2017.