Fair Value Measurements (Details) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Assets
Derivative assets		$ 42		$ 42		$ 57
Assets, Fair Value Disclosure		982		982		747
Total derivative assets, netting adjustment	[1]	(93)		(93)		(82)
Liabilities
Financial Liabilities Fair Value Disclosure		921		921		732
Total derivative liabilities, netting adjustment	[1]	(143)		(143)		(101)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		20	$ (628)	30	$ (622)
Total gains		4	1	16	4
Total settlements		(1)	(1)	(18)	(36)
Transfers into Level 3		0	0	(1)	(2)
Transfers out of Level 3		(2)	650	(6)	678
Ending balance (1)	[2]	21	22	21	22
The amount of total gains for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at the reporting date:		2	11	13	9
Carrying Amount [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	14,861		14,861		9,140
Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	15,994		15,994		9,308
Energy Related Derivative [Member]
Liabilities
Derivative fair value offsets, net		50		50		19
Fair Value, Inputs, Level 1 [Member]
Assets
Assets, Fair Value Disclosure		798		798		609
Liabilities
Financial Liabilities Fair Value Disclosure		7		7		24
Fair Value, Inputs, Level 2 [Member]
Assets
Assets, Fair Value Disclosure		234		234		173
Liabilities
Financial Liabilities Fair Value Disclosure		1,035		1,035		792
Fair Value, Inputs, Level 3 [Member]
Assets
Assets, Fair Value Disclosure		43		43		47
Liabilities
Financial Liabilities Fair Value Disclosure		22		$ 22		17
Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member] | Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Fair value inputs (price per MMBtu)				1.38
Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Fair value inputs (price per MMBtu)				6.09
Fair Value, Measurements, Recurring [Member]
Assets
Corporate equities		748		$ 748		542
Investments, including money market funds (2)	[4]	50		50		66
Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liabilities		15		15		24
Fair Value, Measurements, Recurring [Member] | Energy Related Derivative [Member]
Assets
Derivative asset, netting adjustment	[1],[5],[6]	(93)		(93)		(82)
Derivative assets	[5],[6]	184		184		138
Liabilities
Derivative liabilities, netting adjustment	[1],[5],[6]	(143)		(143)		(101)
Derivative liabilities	[5],[6]	82		82		107
Fair Value, Measurements, Recurring [Member] | IDS Derivative [Member]
Liabilities
Derivative liabilities, netting adjustment	[1]	0		0		0
Derivative liabilities		817		817		601
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Corporate equities		748		748		542
Investments, including money market funds (2)	[4]	50		50		66
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liability		0		0		24
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Energy Related Derivative [Member]
Assets
Derivative asset	[5],[6]	0		0		0
Liabilities
Derivative liability	[5],[6]	0		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | IDS Derivative [Member]
Liabilities
Derivative liability		0		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Corporate equities		0		0		0
Investments, including money market funds (2)	[4]	0		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liability		15		15		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Energy Related Derivative [Member]
Assets
Derivative asset	[5],[6]	234		234		173
Liabilities
Derivative liability	[5],[6]	203		203		191
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | IDS Derivative [Member]
Liabilities
Derivative liability		817		817		601
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Corporate equities		0		0		0
Investments, including money market funds (2)	[4]	0		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liability		0		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Energy Related Derivative [Member]
Assets
Derivative asset	[5],[6]	43		43		47
Liabilities
Derivative liability	[5],[6]	22		22		17
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | IDS Derivative [Member]
Liabilities
Derivative liability		0		0		0
Houston Electric [Member]
Assets
Assets, Fair Value Disclosure		33		33		48
Total derivative assets, netting adjustment		0		0		0
Liabilities
Financial Liabilities Fair Value Disclosure		0		0		24
Total derivative liabilities, netting adjustment		0		0		0
Houston Electric [Member] | Carrying Amount [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	5,018		5,018		4,717
Houston Electric [Member] | Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	5,595		5,595		4,770
Houston Electric [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Assets, Fair Value Disclosure		33		33		48
Liabilities
Financial Liabilities Fair Value Disclosure		0		0		24
Houston Electric [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Assets, Fair Value Disclosure		0		0		0
Liabilities
Financial Liabilities Fair Value Disclosure		0		0		0
Houston Electric [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Assets, Fair Value Disclosure		0		0		0
Liabilities
Financial Liabilities Fair Value Disclosure		0		0		0
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member]
Assets
Investments, including money market funds (2)	[4]	33		33		48
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liabilities		0		0		24
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Investments, including money market funds (2)	[4]	33		33		48
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liability		0		0		24
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Investments, including money market funds (2)	[4]	0		0		0
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liability		0		0		0
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Investments, including money market funds (2)	[4]	0		0		0
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liability		0		0		0
CERC Corp [Member]
Assets
Derivative assets		42		42		57
Assets, Fair Value Disclosure		197		197		152
Total derivative assets, netting adjustment	[1]	(93)		(93)		(82)
Liabilities
Financial Liabilities Fair Value Disclosure		69		69		107
Total derivative liabilities, netting adjustment	[1]	(143)		(143)		(101)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		20	13	30	46
Total gains		4	1	16	4
Total settlements		(1)	(1)	(18)	(36)
Transfers into Level 3		0	0	(1)	(2)
Transfers out of Level 3		(2)	9	(6)	10
Ending balance (1)	[2]	21	22	21	22
The amount of total gains for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at the reporting date:		2	$ 11	13	$ 9
CERC Corp [Member] | Carrying Amount [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities		2,477		2,477		2,371
CERC Corp [Member] | Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities		2,783		2,783		2,488
CERC Corp [Member] | Energy Related Derivative [Member]
Liabilities
Derivative fair value offsets, net		50		50		19
CERC Corp [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Assets, Fair Value Disclosure		13		13		14
Liabilities
Financial Liabilities Fair Value Disclosure		7		7		0
CERC Corp [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Assets, Fair Value Disclosure		234		234		173
Liabilities
Financial Liabilities Fair Value Disclosure		183		183		191
CERC Corp [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Assets, Fair Value Disclosure		43		43		47
Liabilities
Financial Liabilities Fair Value Disclosure		22		$ 22		17
CERC Corp [Member] | Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member] | Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Fair value inputs (price per MMBtu)				1.38
CERC Corp [Member] | Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Fair value inputs (price per MMBtu)				6.09
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member]
Assets
Corporate equities		2		$ 2		2
Investments, including money market funds (2)	[4]	11		11		11
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Energy Related Derivative [Member]
Assets
Derivative asset, netting adjustment	[1],[5],[6]	(93)		(93)		(82)
Derivative assets	[5],[6]	184		184		138
Liabilities
Derivative liabilities, netting adjustment	[1],[5],[6]	(143)		(143)		(101)
Derivative liabilities	[5],[6]	62		62		107
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Corporate equities		2		2		2
Investments, including money market funds (2)	[4]	11		11		11
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Energy Related Derivative [Member]
Assets
Derivative asset	[5],[6]	0		0		0
Liabilities
Derivative liability	[5],[6]	0		0		0
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Corporate equities		0		0		0
Investments, including money market funds (2)	[4]	0		0		0
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Energy Related Derivative [Member]
Assets
Derivative asset	[5],[6]	234		234		173
Liabilities
Derivative liability	[5],[6]	183		183		191
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Corporate equities		0		0		0
Investments, including money market funds (2)	[4]	0		0		0
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Energy Related Derivative [Member]
Assets
Derivative asset	[5],[6]	43		43		47
Liabilities
Derivative liability	[5],[6]	22		22		17
Natural gas inventory [Member] | Fair Value, Measurements, Recurring [Member]
Assets
Hedged portion of natural gas inventory		0		0		1
Liabilities
Fair Value Hedge Liabilities		7		7		0
Natural gas inventory [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Hedged portion of natural gas inventory		0		0		1
Liabilities
Fair Value Hedge Liabilities		7		7		0
Natural gas inventory [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Hedged portion of natural gas inventory		0		0		0
Liabilities
Fair Value Hedge Liabilities		0		0		0
Natural gas inventory [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Hedged portion of natural gas inventory		0		0		0
Liabilities
Fair Value Hedge Liabilities		0		0		0
Natural gas inventory [Member] | CERC Corp [Member] | Fair Value, Measurements, Recurring [Member]
Assets
Hedged portion of natural gas inventory		0		0		1
Liabilities
Fair Value Hedge Liabilities		7		7		0
Natural gas inventory [Member] | CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Hedged portion of natural gas inventory		0		0		1
Liabilities
Fair Value Hedge Liabilities		7		7		0
Natural gas inventory [Member] | CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Hedged portion of natural gas inventory		0		0		0
Liabilities
Fair Value Hedge Liabilities		0		0		0
Natural gas inventory [Member] | CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Hedged portion of natural gas inventory		0		0		0
Liabilities
Fair Value Hedge Liabilities		$ 0		$ 0		$ 0

[1] Amounts represent the impact of legally enforceable master netting arrangements that allow CenterPoint Energy and CERC to settle positive and negative positions and also include cash collateral posted with the same counterparties as follows:   September 30, 2019   December 31, 2018   CenterPoint Energy   CERC   CenterPoint Energy   CERC   (in millions) Cash collateral posted with the same counterparties $ 50
  $ 50
  $ 19
  $ 19

[2] CenterPoint Energy and CERC did not have significant Level 3 sales or purchases during the three or nine months ended September 30, 2019 or 2018.

[3] Includes Securitization Bonds debt.

[4] Amounts are included in Prepaid expenses and other current assets in the Condensed Consolidated Balance Sheets.

[5] Level 1 natural gas derivatives include exchange-traded derivatives cleared by the CME, which deems that financial instruments cleared by the CME are settled daily in connection with posted cash payments. As a result of this exchange rule, CME-related derivatives are considered to have no fair value at the balance sheet date for financial reporting purposes and are presented in Level 1 net of posted cash; however, the derivatives remain outstanding and subject to future commodity price fluctuations until they are settled in accordance with their contractual terms. Derivative transactions cleared on exchanges other than the CME (e.g., the Intercontinental Exchange or ICE) continue to be reported on a gross basis.

[6] Natural gas derivatives include no material amounts related to physical forward transactions with Enable.