Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Current income tax expense (benefit):
Federal	$ 89		$ 32		$ 23
State	9		9		18
Total current expense (benefit)	98		41		41
Deferred income tax expense (benefit):
Federal	(25)		(806)		185
State	73		36		28
Total deferred expense (benefit)	48		(770)		213
Total income tax expense (benefit)	146	[1]	(729)	[2]	254	[3]
Income tax reconciliation [Abstract]
Income before income taxes	$ 514	[1]	$ 1,063	[2]	$ 686	[3]
Federal statutory income tax rate	21.00%	[1]	35.00%	[2]	35.00%	[3]
Expected federal income tax expense	$ 108	[1]	$ 372	[2]	$ 240	[3]
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	22	[1]	26	[2]	27	[3]
Other adjustments	11	[1]	3	[2]	3	[3]
State law change, net of federal income tax	32	[1]	0	[2]	0	[3]
Federal income tax rate reduction	0	[1]	(1,113)	[2]	0	[3]
Excess deferred income tax amortization	(24)	[1]	0	[2]	0	[3]
Other, net	(3)	[1]	(17)	[2]	(16)	[3]
Total	38	[1]	(1,101)	[2]	14	[3]
Total income tax expense (benefit)	$ 146	[1]	$ (729)	[2]	$ 254	[3]
Effective tax rate (in hundredths)	28.00%	[1]	(69.00%)	[2]	37.00%	[3]
Valuation allowance on certain state carryforwards					$ 3
Deferred tax assets:
Benefits and compensation	$ 160		$ 162
Regulatory liabilities	356		347
Loss and credit carryforwards	84		90
Asset retirement obligations	62		68
Other	29		16
Valuation allowance	(18)		(7)
Total deferred tax assets	673		676
Deferred tax liabilities:
Property, plant, and equipment	1,894		1,808
Investment in unconsolidated affiliates	987		927
Regulatory assets	395		473
Investment in marketable securities and indexed debt	478		502
Indexed debt securities derivative	27		13
Other	131		127
Total deferred tax liabilities	3,912		3,850
Net deferred tax liabilities	3,239		3,174
State and Local Jurisdiction [Member]
Increase (decrease) in tax expense resulting from:
State law change, net of federal income tax					6
Deferred tax liabilities:
Operating loss carryforwards	802
Deferred tax assets tax credit carryforwards	18
Houston Electric [Member]
Current income tax expense (benefit):
Federal	109		70		165
State	18		19		18
Total current expense (benefit)	127		89		183
Deferred income tax expense (benefit):
Federal	(38)		(98)		(34)
Total deferred expense (benefit)	(38)		(98)		(34)
Total income tax expense (benefit)	89	[4]	(9)	[5]	149
Income tax reconciliation [Abstract]
Income before income taxes	$ 425	[4]	$ 424	[5]	$ 425
Federal statutory income tax rate	21.00%	[4]	35.00%	[5]	35.00%
Expected federal income tax expense	$ 89	[4]	$ 148	[5]	$ 149
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	14	[4]	12	[5]	12
Federal income tax rate reduction	0	[4]	(158)	[5]	0
Excess deferred income tax amortization	(9)	[4]	0	[5]	0
Other, net	(5)	[4]	(11)	[5]	(12)
Total	0	[4]	(157)	[5]	0
Total income tax expense (benefit)	$ 89	[4]	$ (9)	[5]	$ 149
Effective tax rate (in hundredths)	21.00%	[4]	(2.00%)	[5]	35.00%
Deferred tax assets:
Benefits and compensation	$ 17		$ 28
Regulatory liabilities	205		198
Asset retirement obligations	7		7
Other	12		3
Total deferred tax assets	241		236
Deferred tax liabilities:
Property, plant, and equipment	1,087		1,030
Regulatory assets	177		265
Total deferred tax liabilities	1,264		1,295
Net deferred tax liabilities	1,023		1,059
CERC Corp [Member]
Deferred income tax expense (benefit):
Total deferred expense (benefit)	31		(224)		$ 56
Total income tax expense (benefit)	22		(265)		81
Income tax reconciliation [Abstract]
Income before income taxes	92		319		199
Increase (decrease) in tax expense resulting from:
Total income tax expense (benefit)	22		(265)		81
Deferred tax assets:
Valuation allowance	(18)
CERC Corp [Member] | State and Local Jurisdiction [Member]
Deferred tax liabilities:
Operating loss carryforwards	797
Deferred tax assets tax credit carryforwards	17
CERC Corp [Member] | Internal Revenue Service (IRS) [Member]
Deferred tax liabilities:
Operating loss carryforwards	$ 951
Earliest Tax Year [Member] | State and Local Jurisdiction [Member]
Deferred tax liabilities:
Tax credit carryforward expiration date	Dec. 31, 2019
Earliest Tax Year [Member] | CERC Corp [Member] | State and Local Jurisdiction [Member]
Deferred tax liabilities:
Tax credit carryforward expiration date	Dec. 31, 2019
Latest Tax Year [Member] | State and Local Jurisdiction [Member]
Deferred tax liabilities:
Tax credit carryforward expiration date	Dec. 31, 2038
Latest Tax Year [Member] | CERC Corp [Member] | State and Local Jurisdiction [Member]
Deferred tax liabilities:
Tax credit carryforward expiration date	Dec. 31, 2038
Excess deferred income taxes [Member]
Deferred tax liabilities:
Net regulatory liability			1,300
Net regulatory liabilities gross-up			300
Excess deferred income taxes [Member] | Houston Electric [Member]
Deferred tax liabilities:
Net regulatory liability			829
Net regulatory liabilities gross-up			180
Excess deferred income taxes [Member] | CERC Corp [Member]
Deferred tax liabilities:
Net regulatory liability			478
Net regulatory liabilities gross-up			$ 121
Federal Income Tax Rate Prior To TCJA [Member]
Income tax reconciliation [Abstract]
Federal statutory income tax rate			35.00%
Federal Income Tax Rate Prior To TCJA [Member] | Houston Electric [Member]
Income tax reconciliation [Abstract]
Federal statutory income tax rate			35.00%
Federal Income Tax Rate Prior To TCJA [Member] | CERC Corp [Member]
Income tax reconciliation [Abstract]
Federal statutory income tax rate			35.00%
Federal Income Tax Rate After TCJA [Member]
Income tax reconciliation [Abstract]
Federal statutory income tax rate			21.00%
Federal Income Tax Rate After TCJA [Member] | Houston Electric [Member]
Income tax reconciliation [Abstract]
Federal statutory income tax rate			21.00%
Federal Income Tax Rate After TCJA [Member] | CERC Corp [Member]
Income tax reconciliation [Abstract]
Federal statutory income tax rate			21.00%
Continuing Operations [Member] | CERC Corp [Member]
Current income tax expense (benefit):
Federal	$ (9)		$ (31)		21
State	0		(10)		4
Total current expense (benefit)	(9)		(41)		25
Deferred income tax expense (benefit):
Federal	10		(249)		41
State	21		25		15
Total deferred expense (benefit)	31		(224)		56
Total income tax expense (benefit)	22	[6]	(265)	[7]	81
Income tax reconciliation [Abstract]
Income before income taxes	$ 92	[6]	$ 319	[7]	$ 199
Federal statutory income tax rate	21.00%	[6]	35.00%	[7]	35.00%
Expected federal income tax expense	$ 19	[6]	$ 112	[7]	$ 70
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	5	[6]	6	[7]	4
State law change, net of federal income tax	0	[6]	0	[7]	6
Federal income tax rate reduction	0	[6]	(396)	[7]	0
Excess deferred income tax amortization	(15)	[6]	0	[7]	0
Other, net	2	[6]	(1)	[7]	(1)
Total	3	[6]	(377)	[7]	11
Total income tax expense (benefit)	$ 22	[6]	$ (265)	[7]	$ 81
Effective tax rate (in hundredths)	24.00%	[6]	(83.00%)	[7]	41.00%
Deferred tax assets:
Benefits and compensation	$ 27		$ 27
Regulatory liabilities	150		150
Loss and credit carryforwards	259		288
Asset retirement obligations	54		60
Other	20		18
Valuation allowance	(18)		(7)
Total deferred tax assets	492		536
Deferred tax liabilities:
Property, plant, and equipment	773		745
Regulatory assets	41		38
Other	84		115
Total deferred tax liabilities	898		898
Net deferred tax liabilities	406		362
Discontinued Operations [Member] | CERC Corp [Member]
Current income tax expense (benefit):
Federal	9		31		$ (21)
State	4		11		2
Total current expense (benefit)	13		42		(19)
Deferred income tax expense (benefit):
Federal	29		56		90
State	4		6		10
Total deferred expense (benefit)	33		62		100
Total income tax expense (benefit)	46		104		81
Income tax reconciliation [Abstract]
Income before income taxes	$ 184		$ 265		$ 208
Federal statutory income tax rate	21.00%		35.00%		35.00%
Expected federal income tax expense	$ 39		$ 93		$ 73
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	7		11		8
Total	7		11		8
Total income tax expense (benefit)	$ 46		$ 104		$ 81
Effective tax rate (in hundredths)	25.00%		39.00%		39.00%
Deferred tax liabilities:
Investment in unconsolidated affiliates	$ 0		$ 927
Net deferred tax liabilities	0		927
State Valuation Allowance, net of Federal Income Taxes [Member] | Continuing Operations [Member] | CERC Corp [Member]
Increase (decrease) in tax expense resulting from:
Other adjustments	11	[6]	3	[7]	$ 2
Tax Basis Balance Sheet Adjustment [Member] | Continuing Operations [Member] | CERC Corp [Member]
Increase (decrease) in tax expense resulting from:
Other adjustments	$ 0	[6]	$ 11	[7]	$ 0

[1] Recognized a $32 million deferred tax expense due to state law changes that resulted in remeasurement of state deferred taxes in those jurisdictions. Also recorded an additional $11 million valuation allowance on certain state net operating loss deferred tax assets that are no longer expected to be utilized prior to expiration after the Internal Spin. These items are partially offset by $24 million of amortization of the net regulatory EDIT liability as decreed by regulators in certain jurisdictions beginning in 2018.

[2] Recognized a $1.1 billion deferred tax benefit from the remeasurement of CenterPoint Energy’s ADFIT liability as a result of the enactment of the TCJA on December 22, 2017, which reduced the U.S. corporate income tax rate from 35% to 21%. For additional information on the 2017 impacts of the TCJA, please see the discussion following the deferred tax assets and liabilities table below.

[3] Recognized a $6 million deferred tax expense in 2016 due to Louisiana state law change and recorded an additional $3 million valuation allowance on certain state carryforwards.

[4] Recognized $9 million of amortization of the net regulatory EDIT liability as decreed by regulators in certain jurisdictions beginning in 2018.

[5] Recognized a $158 million deferred tax benefit from the remeasurement of Houston Electric’s ADFIT liability as a result of the enactment of the TCJA on December 22, 2017, which reduced the U.S. corporate income tax rate from 35% to 21%. For additional information on the 2017 impacts of the TCJA, please see the discussion following the deferred tax assets and liabilities table below.

[6] Recorded an additional $11 million valuation allowance on certain state net operating loss deferred tax assets that are no longer expected to be utilized prior to expiration after the Internal Spin. This item is partially offset by $15 million of amortization of the net regulatory EDIT liability in certain jurisdictions as decreed by regulators beginning in 2018.

[7] Recognized a $396 million deferred tax benefit from the remeasurement of CERC’s ADFIT liability as a result of the enactment of the TCJA on December 22, 2017, which reduced the U.S. corporate income tax rate from 35% to 21%. ASC 740 requires tax impacts of changes in tax laws or rates be reported in continuing operations. Therefore, CERC’s federal income tax benefit generated by the remeasurement of the ADFIT liability for Enable during 2017 and state law changes during 2016 associated with its investment in Enable are reported in continuing operations on CERC’s Statements of Consolidated Income. The ADFIT liability associated with CERC’s investment in Enable is reported as discontinued operations on CERC’s Consolidated Balance Sheets.