Fair Value Measurements (Details)		3 Months Ended		6 Months Ended
		Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Fair value amount of Level 1 to Level 2 assets transferred		$ 0		$ 0
Fair value amount of Level 2 to Level 1 assets transferred		0		0
Fair value amount of Level 1 to Level 2 liabilities transferred		0		0
Fair value amount of Level 2 to Level 1 liabilities transferred		0		0
Assets
Total derivative assets, netting adjustment	[1]	(40,000,000)		(40,000,000)		$ (64,000,000)
Total assets		776,000,000		776,000,000		1,199,000,000
Liabilities
Total derivative liabilities, netting adjustment	[1]	(72,000,000)		(72,000,000)		(83,000,000)
Total liabilities		680,000,000		680,000,000		692,000,000
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		(662,000,000)	$ (700,000,000)	(622,000,000)	$ (704,000,000)
Total gains (losses)		(11,000,000)	(6,000,000)	(16,000,000)	0
Total settlements		44,000,000	0	11,000,000	(4,000,000)
Transfers into Level 3		1,000,000	1,000,000	1,000,000	2,000,000
Transfers out of Level 3		0	(7,000,000)	(2,000,000)	(6,000,000)
Ending balance (1)	[2]	(628,000,000)	(712,000,000)	(628,000,000)	(712,000,000)
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:		(9,000,000)	(9,000,000)	(23,000,000)	(2,000,000)
Carrying Amount [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	8,256,000,000		8,256,000,000		8,679,000,000
Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	8,470,000,000		8,470,000,000		9,220,000,000
Natural gas derivatives [Member]
Assets
Derivative fair value offsets, net		32,000,000		32,000,000		19,000,000
Fair Value, Inputs, Level 1 [Member]
Assets
Total assets		656,000,000		656,000,000		1,045,000,000
Liabilities
Total liabilities		1,000,000		1,000,000		0
Fair Value, Inputs, Level 2 [Member]
Assets
Total assets		142,000,000		142,000,000		161,000,000
Liabilities
Total liabilities		105,000,000		105,000,000		96,000,000
Fair Value, Inputs, Level 3 [Member]
Assets
Total assets		18,000,000		18,000,000		57,000,000
Liabilities
Total liabilities		646,000,000		$ 646,000,000		679,000,000
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)				1.04
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)				3.31
Fair Value, Measurements, Recurring [Member]
Assets
Corporate equities		586,000,000		$ 586,000,000		963,000,000
Investments, including money market funds (2)	[4]	70,000,000		70,000,000		68,000,000
Hedged portion of natural gas inventory		0		0		14,000,000
Liabilities
Hedged portion of natural gas inventory		1,000,000		1,000,000		0
Fair Value, Measurements, Recurring [Member] | IDS Derivative [Member]
Liabilities
Derivative liabilities, netting adjustment	[1]	0		0		0
Derivative liabilities		641,000,000		641,000,000		668,000,000
Fair Value, Measurements, Recurring [Member] | Natural gas derivatives [Member]
Assets
Derivative asset, netting adjustment	[1],[5]	(40,000,000)		(40,000,000)		(64,000,000)
Derivative assets	[5]	120,000,000		120,000,000		154,000,000
Liabilities
Derivative liabilities, netting adjustment	[1],[5]	(72,000,000)		(72,000,000)		(83,000,000)
Derivative liabilities	[5]	38,000,000		38,000,000		24,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Corporate equities		586,000,000		586,000,000		963,000,000
Investments, including money market funds (2)	[4]	70,000,000		70,000,000		68,000,000
Hedged portion of natural gas inventory		0		0		14,000,000
Liabilities
Hedged portion of natural gas inventory		1,000,000		1,000,000		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 1 [Member] | Natural gas derivatives [Member]
Assets
Derivative asset	[5]	0		0		0
Liabilities
Derivative liability	[5]	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
Hedged portion of natural gas inventory		0		0		0
Liabilities
Hedged portion of natural gas inventory		0		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | IDS Derivative [Member]
Liabilities
Derivative liability		0		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Natural gas derivatives [Member]
Assets
Derivative asset	[5]	142,000,000		142,000,000		161,000,000
Liabilities
Derivative liability	[5]	105,000,000		105,000,000		96,000,000
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
Hedged portion of natural gas inventory		0		0		0
Liabilities
Hedged portion of natural gas inventory		0		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | IDS Derivative [Member]
Liabilities
Derivative liability		641,000,000		641,000,000		668,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Natural gas derivatives [Member]
Assets
Derivative asset	[5]	18,000,000		18,000,000		57,000,000
Liabilities
Derivative liability	[5]	5,000,000		5,000,000		11,000,000
CERC Corp [Member]
Assets
Total derivative assets, netting adjustment	[1]	(40,000,000)		(40,000,000)		(64,000,000)
Total assets		133,000,000		133,000,000		182,000,000
Liabilities
Total derivative liabilities, netting adjustment	[1]	(72,000,000)		(72,000,000)		(83,000,000)
Total liabilities		39,000,000		39,000,000		24,000,000
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		12,000,000	27,000,000	46,000,000	13,000,000
Total gains (losses)		1,000,000	7,000,000	3,000,000	23,000,000
Total settlements		(1,000,000)	0	(35,000,000)	(4,000,000)
Transfers into Level 3		1,000,000	1,000,000	1,000,000	2,000,000
Transfers out of Level 3		0	(7,000,000)	(2,000,000)	(6,000,000)
Ending balance (1)	[2]	13,000,000	28,000,000	13,000,000	28,000,000
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:		3,000,000	$ 4,000,000	(4,000,000)	$ 21,000,000
CERC Corp [Member] | Carrying Amount [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities		2,722,000,000		2,722,000,000		2,457,000,000
CERC Corp [Member] | Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities		2,876,000,000		2,876,000,000		2,708,000,000
CERC Corp [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Total assets		13,000,000		13,000,000		28,000,000
Liabilities
Total liabilities		1,000,000		1,000,000		0
CERC Corp [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Total assets		142,000,000		142,000,000		161,000,000
Liabilities
Total liabilities		105,000,000		105,000,000		96,000,000
CERC Corp [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Total assets		18,000,000		18,000,000		57,000,000
Liabilities
Total liabilities		5,000,000		5,000,000		11,000,000
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member]
Assets
Corporate equities		2,000,000		2,000,000		3,000,000
Investments, including money market funds (2)	[4]	11,000,000		11,000,000		11,000,000
Hedged portion of natural gas inventory		0		0		14,000,000
Liabilities
Hedged portion of natural gas inventory		1,000,000		1,000,000		0
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Natural gas derivatives [Member]
Assets
Derivative asset, netting adjustment	[1],[5]	(40,000,000)		(40,000,000)		(64,000,000)
Derivative assets	[5]	120,000,000		120,000,000		154,000,000
Liabilities
Derivative liabilities, netting adjustment	[1],[5]	(72,000,000)		(72,000,000)		(83,000,000)
Derivative liabilities	[5]	38,000,000		38,000,000		24,000,000
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Corporate equities		2,000,000		2,000,000		3,000,000
Investments, including money market funds (2)	[4]	11,000,000		11,000,000		11,000,000
Hedged portion of natural gas inventory		0		0		14,000,000
Liabilities
Hedged portion of natural gas inventory		1,000,000		1,000,000		0
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Natural gas derivatives [Member]
Assets
Derivative asset	[5]	0		0		0
Liabilities
Derivative liability	[5]	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
Hedged portion of natural gas inventory		0		0		0
Liabilities
Hedged portion of natural gas inventory		0		0		0
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Natural gas derivatives [Member]
Assets
Derivative asset	[5]	142,000,000		142,000,000		161,000,000
Liabilities
Derivative liability	[5]	105,000,000		105,000,000		96,000,000
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
Hedged portion of natural gas inventory		0		0		0
Liabilities
Hedged portion of natural gas inventory		0		0		0
CERC Corp [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Natural gas derivatives [Member]
Assets
Derivative asset	[5]	18,000,000		18,000,000		57,000,000
Liabilities
Derivative liability	[5]	5,000,000		5,000,000		11,000,000
Houston Electric [Member]
Assets
Total derivative assets, netting adjustment		0		0		0
Total assets		52,000,000		52,000,000		51,000,000
Houston Electric [Member] | Carrying Amount [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	4,919,000,000		4,919,000,000		4,753,000,000
Houston Electric [Member] | Fair Value [Member]
Estimated Fair Value of Financial Instruments
Long-term debt, including current maturities	[3]	4,991,000,000		4,991,000,000		5,034,000,000
Houston Electric [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Total assets		52,000,000		52,000,000		51,000,000
Houston Electric [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Total assets		0		0		0
Houston Electric [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Total assets		0		0		0
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member]
Assets
Investments, including money market funds (2)	[4]	52,000,000		52,000,000		51,000,000
Houston Electric [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Investments, including money market funds (2)	[4]	52,000,000		52,000,000		51,000,000
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 3 [Member]
Assets
Investments, including money market funds (2)	[4]	$ 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 of $32 million and $19 million as of June 30, 2018 and December 31, 2017, respectively, posted with the same counterparties.

[2] CenterPoint Energy and CERC did not have significant Level 3 sales or purchases during either of the three or six months ended June 30, 2018 or 2017.

[3] Includes Securitization Bond debt.

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

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