Derivative Instruments Derivatives and Hedging (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weather Hedges Term	10 years
Not Designated as Hedging Instrument [Member] \| Interest Rate Contract [Member]
Derivative Liability, Notional Amount	$ 84	$ 0
CenterPoint Energy Resources Corp.
Weather Hedges Term	10 years
CenterPoint Energy Houston Electric, LLC \| Not Designated as Hedging Instrument [Member] \| Interest Rate Contract [Member]
Derivative Liability, Notional Amount	$ 0	0
Cash Flow Hedging [Member] \| Interest Rate Contract [Member]
Derivative Liability, Notional Amount	0	450
Cash Flow Hedging [Member] \| CenterPoint Energy Houston Electric, LLC \| Interest Rate Contract [Member]
Derivative Liability, Notional Amount	0	450
Natural Gas Distribution [Member] \| 2019 to 2020 [Member]
Weather Hedge, Bilateral Cap Amount	8
Natural Gas Distribution [Member] \| 2019 to 2020 [Member] \| CenterPoint Energy Resources Corp.
Weather Hedge, Bilateral Cap Amount	8
Natural Gas Distribution [Member] \| 2018 to 2019 [Member]
Weather Hedge, Bilateral Cap Amount	9
Natural Gas Distribution [Member] \| 2018 to 2019 [Member] \| CenterPoint Energy Resources Corp.
Weather Hedge, Bilateral Cap Amount	9
Natural Gas Distribution [Member] \| 2017 to 2018 [Member]
Weather Hedge, Bilateral Cap Amount	8
Natural Gas Distribution [Member] \| 2017 to 2018 [Member] \| CenterPoint Energy Resources Corp.
Weather Hedge, Bilateral Cap Amount	8
Electric Transmission & Distribution [Member] \| 2019 to 2020 [Member]
Weather Hedge, Bilateral Cap Amount	7
Electric Transmission & Distribution [Member] \| 2018 to 2019 [Member]
Weather Hedge, Bilateral Cap Amount	8
Electric Transmission & Distribution [Member] \| 2017 to 2018 [Member]
Weather Hedge, Bilateral Cap Amount	9
Electric Transmission & Distribution [Member] \| 2016 to 2017 [Member]
Weather Hedge, Bilateral Cap Amount	9
Sales [Member] \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	8	(4)	$ (1)
Sales [Member] \| CenterPoint Energy Resources Corp. \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	2	(2)	0
Sales [Member] \| Natural Gas Distribution [Member] \| 2019 to 2020 [Member] \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	2	0	0
Sales [Member] \| Natural Gas Distribution [Member] \| 2019 to 2020 [Member] \| CenterPoint Energy Resources Corp. \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	2	0	0
Sales [Member] \| Natural Gas Distribution [Member] \| 2018 to 2019 [Member] \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	0	0	0
Sales [Member] \| Natural Gas Distribution [Member] \| 2018 to 2019 [Member] \| CenterPoint Energy Resources Corp. \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	0	0	0
Sales [Member] \| Natural Gas Distribution [Member] \| 2017 to 2018 [Member] \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	0	(2)	0
Sales [Member] \| Natural Gas Distribution [Member] \| 2017 to 2018 [Member] \| CenterPoint Energy Resources Corp. \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	0	(2)	0
Sales [Member] \| Electric Transmission & Distribution [Member] \| 2019 to 2020 [Member] \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	3	0	0
Sales [Member] \| Electric Transmission & Distribution [Member] \| 2018 to 2019 [Member] \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	3	0	0
Sales [Member] \| Electric Transmission & Distribution [Member] \| 2017 to 2018 [Member] \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	0	(2)	0
Sales [Member] \| Electric Transmission & Distribution [Member] \| 2016 to 2017 [Member] \| Weather Hedge Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 0	$ (1)

Represents amount of bilateral cap related to weather hedges.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Period of time used as the basis for weather hedges entered into by the company.

+ References

No definition available.

+ Details

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- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

+ Details

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- Definition

Nominal or face amount used to calculate payments on the derivative liability.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

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- Details

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