Derivative Instruments Summary of Derivative Activity (Details) $ in Millions		12 Months Ended
		Dec. 31, 2018 USD ($) Bcf	Dec. 31, 2017 USD ($) Bcf		Dec. 31, 2016 USD ($)
Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative gross volume notional amount (in Bcf) | Bcf		1,674	1,795
Gross Amounts Recognized	[1]	$ 12	$ 111
Gross Amounts Offset in the Consolidated Balance Sheets		19	19
Net Amount Presented in the Consolidated Balance Sheets	[2]	31	130
Derivative Assets Fair Value		220	218
Derivative Liabilities Fair Value		833	775
Derivative Asset		57	80
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		1	14
Income Statement Impact of Derivative Activity [Abstract]
Total amounts presented in the statements of income in which the effects of hedges are recorded	[3]	4,364	3,785		$ 1,983
Gain (loss) on derivative instruments not designated as hedging instruments		(123)	260		(431)
Derivative, Credit Risk Related Contingent Features [Abstract]
Aggregate fair value of derivatives containing material adverse change provisions in a net liability position		1	2
Fair value of collateral already posted		0	0
Additional collateral required to be posted if credit risk contingent features triggered		0	2
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[4]	138	154
Energy Marketers [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[4]	24	45
Retail End Users [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[4],[5]	114	109
External Credit Rating, Investment Grade [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[6]	41	23
External Credit Rating, Investment Grade [Member] | Energy Marketers [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[6]	11	6
External Credit Rating, Investment Grade [Member] | Retail End Users [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[5],[6]	30	17
Current Assets [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset	[2]	100	110
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		1	14
Gross Amounts Recognized	[1]	166	165
Gross Amounts Offset		(66)	(55)
Other Noncurrent Assets [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset	[2]	38	44
Gross Amounts Recognized	[1]	54	53
Gross Amounts Offset		(16)	(9)
Current Liabilities [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Gross Amounts Recognized	[1]	(183)	(83)
Gross Amounts Offset		81	63
Derivative Liability	[2]	(102)	(20)
Other Noncurrent Liabilities [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Gross Amounts Recognized	[1]	(25)	(24)
Gross Amounts Offset		20	20
Derivative Liability	[2]	(5)	(4)
Not Designated as Hedging Instrument [Member] | Current Liabilities [Member] | IDS Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value		0	0
Derivative Liabilities Fair Value		$ 601	$ 668
Long [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative gross volume notional amount (in Bcf) | Bcf		140	224
Houston Electric [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value		$ 0	$ 0
Derivative Liabilities Fair Value		$ 24	$ 0
CERC Corp [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative gross volume notional amount (in Bcf) | Bcf		1,674	1,795
Gross Amounts Recognized	[1]	$ 12	$ 111
Gross Amounts Offset in the Consolidated Balance Sheets		19	19
Net Amount Presented in the Consolidated Balance Sheets	[2]	31	130
CERC Corp [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value		220	218
Derivative Liabilities Fair Value		208	107
Derivative Asset		57	80
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		1	14
Income Statement Impact of Derivative Activity [Abstract]
Total amounts presented in the statements of income in which the effects of hedges are recorded		4,364	3,785		1,983
Gain (loss) on derivative instruments not designated as hedging instruments		107	211		(18)
Derivative, Credit Risk Related Contingent Features [Abstract]
Aggregate fair value of derivatives containing material adverse change provisions in a net liability position		1	2
Fair value of collateral already posted		0	0
Additional collateral required to be posted if credit risk contingent features triggered		0	2
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[4]	138	154
CERC Corp [Member] | Energy Marketers [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[4]	24	45
CERC Corp [Member] | Retail End Users [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[4],[5]	114	109
CERC Corp [Member] | External Credit Rating, Investment Grade [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[6]	41	23
CERC Corp [Member] | External Credit Rating, Investment Grade [Member] | Energy Marketers [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties		11	6	[6]
CERC Corp [Member] | External Credit Rating, Investment Grade [Member] | Retail End Users [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total credit risk of counterparties	[5]	30	17	[6]
CERC Corp [Member] | Current Assets [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset	[2]	100	110
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of Hedged Item		1	14
Gross Amounts Recognized	[1]	166	165
Gross Amounts Offset		(66)	(55)
CERC Corp [Member] | Other Noncurrent Assets [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset	[2]	38	44
Gross Amounts Recognized	[1]	54	53
Gross Amounts Offset		(16)	(9)
CERC Corp [Member] | Current Liabilities [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Gross Amounts Recognized	[1]	(183)	(83)
Gross Amounts Offset		81	63
Derivative Liability	[2]	(102)	(20)
CERC Corp [Member] | Other Noncurrent Liabilities [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Gross Amounts Recognized	[1]	(25)	(24)
Gross Amounts Offset		20	20
Derivative Liability	[2]	(5)	(4)
CERC Corp [Member] | Not Designated as Hedging Instrument [Member] | Current Assets [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value	[7],[8],[9]	103	114
Derivative Liabilities Fair Value	[7],[8],[9]	3	4
CERC Corp [Member] | Not Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value	[7],[8],[9]	38	44
Derivative Liabilities Fair Value	[7],[8],[9]	0	0
CERC Corp [Member] | Not Designated as Hedging Instrument [Member] | Current Liabilities [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value	[7],[8],[9]	62	38
Derivative Liabilities Fair Value	[7],[8],[9]	173	78
CERC Corp [Member] | Not Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value	[7],[8],[9]	16	9
Derivative Liabilities Fair Value	[7],[8],[9]	$ 25	$ 24
CERC Corp [Member] | Long [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative gross volume notional amount (in Bcf) | Bcf		140	224
Cash Flow Hedging [Member] | Houston Electric [Member] | Designated as Hedging Instrument [Member] | Current Liabilities [Member] | Interest Rate Contract [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value		$ 0	$ 0
Derivative Liabilities Fair Value		24	0
Fair Value Hedging [Member] | Current Assets [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset		57	80
Fair Value Hedging [Member] | CERC Corp [Member] | Current Assets [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset		57	80
Fair Value Hedging [Member] | CERC Corp [Member] | Designated as Hedging Instrument [Member] | Current Liabilities [Member] | Energy Related Derivative [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets Fair Value	[7],[8],[9]	1	13
Derivative Liabilities Fair Value	[7],[8],[9]	7	1
Gains (Losses) in Revenue [Member] | CERC Corp [Member] | Energy Related Derivative [Member]
Income Statement Impact of Derivative Activity [Abstract]
Gain (loss) on derivative instruments not designated as hedging instruments		107	211		(18)
Natural Gas Expenses [Member] | Fair Value Hedging [Member] | Energy Related Derivative [Member]
Income Statement Impact of Derivative Activity [Abstract]
Change in unrealized gain (loss) on fair value hedging instruments	[3]	(13)	14		0
Amounts excluded from effectiveness testing recognized in earnings immediately (1)	[3],[10]	(149)	(67)		70
Natural Gas Expenses [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] | Energy Related Derivative [Member]
Income Statement Impact of Derivative Activity [Abstract]
Change in unrealized gain (loss) on fair value hedging instruments	[3]	13	(14)		0
Natural Gas Expenses [Member] | Fair Value Hedging [Member] | CERC Corp [Member] | Energy Related Derivative [Member]
Income Statement Impact of Derivative Activity [Abstract]
Change in unrealized gain (loss) on fair value hedging instruments	[3]	(13)	14		0
Amounts excluded from effectiveness testing recognized in earnings immediately (1)	[3],[10]	(149)	(67)		70
Natural Gas Expenses [Member] | Fair Value Hedging [Member] | CERC Corp [Member] | Designated as Hedging Instrument [Member] | Energy Related Derivative [Member]
Income Statement Impact of Derivative Activity [Abstract]
Change in unrealized gain (loss) on fair value hedging instruments	[3]	13	(14)		0
Gains (Losses) in Other Income (Expense) [Member] | Interest Rate Contract [Member]
Income Statement Impact of Derivative Activity [Abstract]
Gain (loss) on derivative instruments not designated as hedging instruments		2	0		0
Gains (Losses) in Other Income (Expense) [Member] | IDS Derivative [Member]
Income Statement Impact of Derivative Activity [Abstract]
Gain (loss) on derivative instruments not designated as hedging instruments		$ (232)	$ 49		$ (413)

[1] Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.

[2] The derivative assets and liabilities on the Consolidated Balance Sheets exclude accounts receivable or accounts payable that, should they exist, could be used as offsets to these balances in the event of a default.

[3] Income statement impact associated with cash flow hedge activity is related to gains and losses reclassified from Accumulated other comprehensive income into income. Amounts are immaterial for the Registrants for the years ended December 31, 2018, 2017 and 2016, respectively.

[4] The amounts reflected in the table above were not impacted by collateral netting.

[5] End users are comprised primarily of customers who have contracted to fix the price of a portion of their physical gas requirements for future periods.

[6] “Investment grade” is primarily determined using publicly available credit ratings and considers credit support (including parent company guarantees) and collateral (including cash and standby letters of credit). For unrated counterparties, CenterPoint Energy and CERC determine a synthetic credit rating by performing financial statement analysis and consider contractual rights and restrictions and collateral.

[7] Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable.

[8] Natural gas contracts are presented on a net basis in the Consolidated Balance Sheets as they are subject to master netting arrangements. This netting applies to all undisputed amounts due or past due and causes derivative assets (liabilities) to be ultimately presented net in a liability (asset) account within the Consolidated Balance Sheets. The net of total non-trading natural gas derivative assets and liabilities is detailed in the Offsetting of Natural Gas Derivative Assets and Liabilities table below

[9] The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 1,674 Bcf or a net 140 Bcf long position and 1,795 Bcf or a net 224 Bcf long position as of December 31, 2018 and 2017, respectively. Certain natural gas contracts hedge basis risk only and lack a fixed price exposure.

[10] Upon adoption of ASU 2017-12 effective January 1, 2018 (see Note 2 for additional information), CenterPoint Energy and CERC elected to exclude from their assessment of hedge effectiveness the natural gas market price difference between locations of the hedged inventory and the delivery location specified in the hedge instruments. Prior to the adoption of this accounting guidance, the timing difference between the spot price and the futures price, as well as the difference between the timing of the settlement of the futures and the valuation of the underlying physical commodity, was excluded from the assessment of effectiveness for CenterPoint Energy’s and CERC’s existing fair value hedges and will continue to be excluded from the assessment of hedge effectiveness. CenterPoint Energy and CERC elected to continue to immediately recognize amounts excluded from hedge effectiveness in their respective Statements of Consolidated Income.