Fair Value Measurements (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		$ 823		$ 823		$ 732
Assets
Derivative assets		48		48		57
Assets, Fair Value Disclosure		898		898		747
Total derivative assets, netting adjustment	[1]	(103)		(103)		(82)
Liabilities
Total derivative liabilities, netting adjustment	[1]	(139)		(139)		(101)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		13	$ (662)	30	$ (622)
Total gains (losses)		13	(11)	12	(16)
Total settlements		(2)	44	(17)	11
Transfers into Level 3		(2)	1	(1)	1
Transfers out of Level 3		(2)	0	(4)	(2)
Ending balance (1)	[2]	20	(628)	20	(628)
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at the reporting date:		9	(9)	6	(23)
Carrying Amount [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	14,587		14,587		9,140
Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	15,438		15,438		9,308
Energy Related Derivative [Member]
Liabilities
Derivative fair value offsets, net		36		36		19
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		9		9		24
Assets
Assets, Fair Value Disclosure		753		753		609
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		940		940		792
Assets
Assets, Fair Value Disclosure		215		215		173
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		13		13		17
Assets
Assets, Fair Value Disclosure		33		$ 33		47
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)				1.62
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)				5.64
Fair Value, Measurements, Recurring [Member]
Assets
Corporate equities		690		$ 690		542
Investments, including money market funds (2)	[4]	63		63		66
Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member]
Liabilities
Derivative liabilities		8		8		24
Fair Value, Measurements, Recurring [Member] | Energy Related Derivative [Member]
Assets
Derivative asset, netting adjustment	[1],[5],[6]	(103)		(103)		(82)
Derivative assets	[5],[6]	145		145		138
Liabilities
Derivative liabilities, netting adjustment	[1],[5],[6]	(139)		(139)		(101)
Derivative liabilities	[5],[6]	51		51		107
Fair Value, Measurements, Recurring [Member] | IDS Derivative [Member]
Liabilities
Derivative liabilities, netting adjustment	[1]	0		0		0
Derivative liabilities		755		755		601
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Corporate equities		690		690		542
Investments, including money market funds (2)	[4]	63		63		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		8		8		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Energy Related Derivative [Member]
Assets
Derivative asset	[5],[6]	215		215		173
Liabilities
Derivative liability	[5],[6]	177		177		191
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | IDS Derivative [Member]
Liabilities
Derivative liability		755		755		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]	33		33		47
Liabilities
Derivative liability	[5],[6]	13		13		17
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | IDS Derivative [Member]
Liabilities
Derivative liability		0		0		0
Houston Electric [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		0		0		24
Assets
Assets, Fair Value Disclosure		47		47		48
Total derivative assets, netting adjustment		0		0		0
Liabilities
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]	5,165		5,165		4,717
Houston Electric [Member] | Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	5,583		5,583		4,770
Houston Electric [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		0		0		24
Assets
Assets, Fair Value Disclosure		47		47		48
Houston Electric [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		0		0		0
Assets
Assets, Fair Value Disclosure		0		0		0
Houston Electric [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		0		0		0
Assets
Assets, Fair Value Disclosure		0		0		0
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member]
Assets
Investments, including money market funds (2)	[4]	47		47		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]	47		47		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]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		44		44		107
Assets
Derivative assets		48		48		57
Assets, Fair Value Disclosure		159		159		152
Total derivative assets, netting adjustment	[1]	(103)		(103)		(82)
Liabilities
Total derivative liabilities, netting adjustment	[1]	(139)		(139)		(101)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		13	12	30	46
Total gains (losses)		13	1	12	3
Total settlements		(2)	(1)	(17)	(35)
Transfers into Level 3		(2)	1	(1)	1
Transfers out of Level 3		(2)	0	(4)	(2)
Ending balance (1)	[2]	20	13	20	13
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at the reporting date:		9	$ 3	6	$ (4)
CERC Corp [Member] | Carrying Amount [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities		2,397		2,397		2,371
CERC Corp [Member] | Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities		2,641		2,641		2,488
CERC Corp [Member] | Energy Related Derivative [Member]
Liabilities
Derivative fair value offsets, net		36		36		19
CERC Corp [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		9		9		0
Assets
Assets, Fair Value Disclosure		14		14		14
CERC Corp [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		161		161		191
Assets
Assets, Fair Value Disclosure		215		215		173
CERC Corp [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Financial Liabilities Fair Value Disclosure		13		13		17
Assets
Assets, Fair Value Disclosure		33		$ 33		47
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)				1.62
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)				5.64
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member]
Assets
Corporate equities		3		$ 3		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]	(103)		(103)		(82)
Derivative assets	[5],[6]	145		145		138
Liabilities
Derivative liabilities, netting adjustment	[1],[5],[6]	(139)		(139)		(101)
Derivative liabilities	[5],[6]	35		35		107
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Corporate equities		3		3		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]	215		215		173
Liabilities
Derivative liability	[5],[6]	161		161		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]	33		33		47
Liabilities
Derivative liability	[5],[6]	13		13		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		9		9		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		9		9		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		9		9		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		9		9		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:   June 30, 2019   December 31, 2018   CenterPoint Energy   CERC   CenterPoint Energy   CERC   (in millions) Cash collateral posted with the same counterparties $ 36
  $ 36
  $ 19
  $ 19

[2] CenterPoint Energy and CERC did not have significant Level 3 sales or purchases during the three or six months ended June 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.