Regulatory Matters (Details) - USD ($) $ in Millions				3 Months Ended		9 Months Ended
		Sep. 16, 2019	Apr. 05, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Securitized regulatory assets				$ 821.0		$ 821.0		$ 1,059.0
Unrecognized equity return (2)	[1]			(175.0)		(175.0)		(213.0)
Unamortized loss on reacquired debt (3)	[2]			63.0		63.0		68.0
Regulatory assets				2,194.0		2,194.0		1,967.0
Total regulatory assets				2,212.0		2,212.0		2,044.0
Regulatory liabilities				3,481.0		3,481.0		2,525.0
Total regulatory liabilities				3,512.0		3,512.0		2,563.0
Total regulatory assets and liabilities, net				(1,300.0)		(1,300.0)		(519.0)
Amount of allowed equity return on the true-up balance that was recognized in the period				14.0	$ 17.0	38.0	$ 62.0
Houston Electric [Member]
Securitized regulatory assets				821.0		821.0		1,059.0
Unrecognized equity return (2)	[1]			(175.0)		(175.0)		(213.0)
Unamortized loss on reacquired debt (3)	[2]			63.0		63.0		68.0
Regulatory assets				951.0		951.0		1,124.0
Total regulatory assets				951.0		951.0		1,124.0
Regulatory liabilities				1,295.0		1,295.0		1,298.0
Total regulatory liabilities				1,295.0		1,295.0		1,315.0
Total regulatory assets and liabilities, net				(344.0)		(344.0)		(191.0)
Amount of allowed equity return on the true-up balance that was recognized in the period				14.0	$ 17.0	38.0	$ 62.0
CERC Corp [Member]
Securitized regulatory assets				0.0		0.0		0.0
Unrecognized equity return (2)				0.0		0.0		0.0
Unamortized loss on reacquired debt (3)				0.0		0.0		0.0
Regulatory assets				189.0		189.0		181.0
Total regulatory assets				207.0		207.0		258.0
Regulatory liabilities				1,221.0		1,221.0		1,227.0
Total regulatory liabilities				1,249.0		1,249.0		1,248.0
Total regulatory assets and liabilities, net				(1,042.0)		(1,042.0)		(990.0)
Hurricane Harvey [Member]
Regulatory assets	[2]			68.0		68.0		68.0
Hurricane Harvey [Member] | Houston Electric [Member]
Regulatory assets	[2]			64.0		64.0		64.0
Hurricane Harvey [Member] | CERC Corp [Member]
Regulatory assets	[2]			4.0		4.0		4.0
Prepaid expenses and other current assets [Member]
Current regulatory assets (1)	[3]			18.0		18.0		77.0
Prepaid expenses and other current assets [Member] | Houston Electric [Member]
Current regulatory assets (1)	[3]			0.0		0.0		0.0
Prepaid expenses and other current assets [Member] | CERC Corp [Member]
Current regulatory assets (1)	[3]			18.0		18.0		77.0
Other current liabilities [Member]
Current regulatory liabilities (6)	[4]			31.0		31.0		38.0
Other current liabilities [Member] | Houston Electric [Member]
Current regulatory liabilities (6)	[4]			0.0		0.0		17.0
Other current liabilities [Member] | CERC Corp [Member]
Current regulatory liabilities (6)	[4]			28.0		28.0		21.0
Asset Retirement Obligation Costs [Member]
Regulatory assets	[2]			139.0		139.0		109.0
Asset Retirement Obligation Costs [Member] | Houston Electric [Member]
Regulatory assets	[2]			25.0		25.0		24.0
Asset Retirement Obligation Costs [Member] | CERC Corp [Member]
Regulatory assets	[2]			92.0		92.0		85.0
Pension and Other Postretirement Plans Costs [Member]
Regulatory assets	[2]			683.0		683.0		725.0
Pension and Other Postretirement Plans Costs [Member] | Houston Electric [Member]
Regulatory assets	[2]			35.0		35.0		33.0
Pension and Other Postretirement Plans Costs [Member] | CERC Corp [Member]
Regulatory assets	[2]			27.0		27.0		30.0
Amounts related to TCJA [Member]
Regulatory assets	[2],[5]			30.0		30.0		33.0
Amounts related to TCJA [Member] | Houston Electric [Member]
Regulatory assets	[2],[5]			23.0		23.0		23.0
Amounts related to TCJA [Member] | CERC Corp [Member]
Regulatory assets	[2],[5]			7.0		7.0		10.0
Other Regulatory Assets (Liabilities) [Member]
Regulatory assets				411.0		411.0		37.0
Other regulatory assets-not earning a return (5)	[6]			154.0		154.0		81.0
Other Regulatory Assets (Liabilities) [Member] | Houston Electric [Member]
Regulatory assets				30.0		30.0		11.0
Other regulatory assets-not earning a return (5)	[6]			65.0		65.0		55.0
Other Regulatory Assets (Liabilities) [Member] | CERC Corp [Member]
Regulatory assets				13.0		13.0		26.0
Other regulatory assets-not earning a return (5)	[6]			46.0		46.0		26.0
Amounts related to TCJA [Member]
Regulatory liabilities	[5]			1,606.0		1,606.0		1,323.0
Amounts related to TCJA [Member] | Houston Electric [Member]
Regulatory liabilities	[5]			830.0		830.0		847.0
Amounts related to TCJA [Member] | CERC Corp [Member]
Regulatory liabilities	[5]			449.0		449.0		476.0
Removal Costs [Member]
Regulatory liabilities				1,430.0		1,430.0		886.0
Removal Costs [Member] | Houston Electric [Member]
Regulatory liabilities				259.0		259.0		269.0
Removal Costs [Member] | CERC Corp [Member]
Regulatory liabilities				634.0		634.0		617.0
Other Regulatory Assets (Liabilities) [Member]
Regulatory liabilities				445.0		445.0		316.0
Other Regulatory Assets (Liabilities) [Member] | Houston Electric [Member]
Regulatory liabilities				206.0		206.0		182.0
Other Regulatory Assets (Liabilities) [Member] | CERC Corp [Member]
Regulatory liabilities				$ 138.0		$ 138.0		$ 134.0
CenterPoint Energy Houston Electric 2019 Rate Case [Member]
Requested revenue increase			$ 194.0
Rate Base			$ 6,400.0
Requested Debt Capital Structure, Percentage			50.00%
Requested Equity Capital Structure, Percentage			50.00%
Requested Return on Equity, Percentage			10.40%
Public Utility Commission of Texas [Member] | Administrative Law Judge Proposal for Decision [Member]
Requested revenue increase		$ 2.6
Rate Base disallowance of assets		120.0
Excess deferred income taxes on securitized assets		$ 158.0

[1] The unrecognized equity return will be recognized as it is recovered in rates through 2024. 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.   Three Months Ended September 30,   Nine Months Ended September 30,   2019   2018   2019   2018   CenterPoint Energy   Houston Electric   CenterPoint Energy   Houston Electric   CenterPoint Energy   Houston Electric   CenterPoint Energy   Houston Electric   (in millions) Allowed equity return recognized $ 14
  $ 14
  $ 17
  $ 17
  $ 38
  $ 38
  $ 62
  $ 62

[2] Substantially all of these regulatory assets are not earning a return.

[3] Current regulatory assets are included in Prepaid expenses and other current assets in the Registrants’ respective 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] The EDIT and deferred revenues will be recovered or refunded to customers as required by tax and regulatory authorities.

[6] Regulatory assets acquired in the Merger and not earning a return were recorded at fair value as of the Merger Date. Such fair value adjustments are recognized over time until the regulatory asset is recovered.