Reportable Segments (Details) - USD ($) $ in Millions		3 Months Ended													12 Months Ended
		Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016		Sep. 04, 2018
Segment Reporting Information [Line Items]
Revenues		$ 3,036		$ 2,212	$ 2,186	$ 3,155	$ 2,638		$ 2,098		$ 2,143		$ 2,735		$ 10,589		$ 9,614		$ 7,528
Depreciation and Amortization															1,243		1,036		1,126
Operating Income (Loss)		167		226	187	251	308	[1]	297	[1]	240	[1]	291	[1]	831		1,136		1,023
Total Assets		27,009					22,736								27,009		22,736		21,829
Expenditures for Long-Lived Assets															1,720		1,494		1,406
Capital expenditures per Statements of Consolidated Cash Flows															1,651		1,426		1,414
Midstream Investments’ equity earnings, net															307		265		208
Total regulatory assets		2,044					2,477								2,044		2,477
Enable Midstream Partners [Member]
Segment Reporting Information [Line Items]
Midstream Investments’ equity earnings, net	[2]														307		265		208
Electric Transmission & Distribution [Member]
Segment Reporting Information [Line Items]
Revenues	[3]														3,232		2,997		3,060
Depreciation and Amortization															917		724		838
Operating Income (Loss)															623		636		653
Expenditures for Long-Lived Assets															952		924		858
Electric Transmission & Distribution [Member] | Affiliates of NRG Energy, Inc. [Member]
Segment Reporting Information [Line Items]
Revenues															705		713		698
Electric Transmission & Distribution [Member] | Affiliates of Vistra Energy Corp. [Member]
Segment Reporting Information [Line Items]
Revenues															251		229		220
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues															2,931		2,606		2,380
Depreciation and Amortization															277		260		242
Operating Income (Loss)															266		348		321
Expenditures for Long-Lived Assets															638		523		510
Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues															4,411		3,997		2,073
Depreciation and Amortization															16		19		7
Operating Income (Loss)															(47)		126		21
Expenditures for Long-Lived Assets															20		11		5
Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues	[4]														0		0		0
Depreciation and Amortization	[4]														0		0		0
Operating Income (Loss)	[4]														0		0		0
Expenditures for Long-Lived Assets	[4]														0		0		0
Midstream Investments [Member] | Enable Midstream Partners [Member]
Segment Reporting Information [Line Items]
Midstream Investments’ equity earnings, net															307		265		208
Other Operations [Member]
Segment Reporting Information [Line Items]
Revenues															15		14		15
Depreciation and Amortization															33		33		39
Operating Income (Loss)															(11)		26		28
Expenditures for Long-Lived Assets															110		36		33
Operating Segments [Member] | Electric Transmission & Distribution [Member]
Segment Reporting Information [Line Items]
Total Assets		10,509					10,292								10,509		10,292		10,211
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Total Assets		6,956					6,608								6,956		6,608		6,099
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Total Assets		1,558					1,521								1,558		1,521		1,102
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Total Assets	[4]	2,482					2,472								2,482		2,472		2,505
Operating Segments [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Total Assets	[5]	6,156					2,497								6,156		2,497		2,681
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues															(146)		(85)		(55)
Total Assets		(652)					(654)								(652)		(654)		(769)
Intersegment Eliminations [Member] | Electric Transmission & Distribution [Member]
Segment Reporting Information [Line Items]
Revenues															0		0		0
Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues															(36)		(33)		(29)
Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues															(110)		(52)		(26)
Intersegment Eliminations [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues	[4]														0		0		0
Intersegment Eliminations [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Revenues															0		0		0
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Expenditures for Long-Lived Assets															(69)		(68)		8
Pension and Other Postretirement Plans Costs [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Total regulatory assets		665					600								665		600		759
Cash and Cash Equivalents [Member]
Segment Reporting Information [Line Items]
Temporary investments		3,900													3,900
Houston Electric [Member]
Segment Reporting Information [Line Items]
Revenues		728		897	854	755	765		843		752		638		3,234		2,998		3,059
Depreciation and Amortization															917		724		838
Operating Income (Loss)		98		$ 227	$ 181	$ 119	127	[1]	$ 254	[1]	$ 171	[1]	$ 85	[1]	625		637		652
Total Assets		10,507					10,292								10,507		10,292
Capital expenditures per Statements of Consolidated Cash Flows															922		875		862
Total regulatory assets		1,124					1,570								1,124		1,570
Houston Electric [Member] | Electric Transmission & Distribution [Member] | Affiliates of NRG Energy, Inc. [Member]
Segment Reporting Information [Line Items]
Revenues															705		713		698
Houston Electric [Member] | Electric Transmission & Distribution [Member] | Affiliates of Vistra Energy Corp. [Member]
Segment Reporting Information [Line Items]
Revenues															251		229		220
CERC Corp [Member]
Segment Reporting Information [Line Items]
Revenues															7,343		6,603		4,454
Depreciation and Amortization															293		279		249
Operating Income (Loss)															222		467		341
Total Assets		8,214	[6]				10,112								8,214	[6]	10,112		9,218
Investment in unconsolidated affiliates - discontinued operations		0					2,472								0		2,472
Expenditures for Long-Lived Assets															658		534		515
Capital expenditures per Statements of Consolidated Cash Flows															633		513		517
Total regulatory assets		258					311								258		311
CERC Corp [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues															2,931		2,606		2,380
Depreciation and Amortization															277		260		242
Operating Income (Loss)															266		348		321
Expenditures for Long-Lived Assets															638		523		510
CERC Corp [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues															4,411		3,997		2,073
Depreciation and Amortization															16		19		7
Operating Income (Loss)															(47)		126		21
Expenditures for Long-Lived Assets															20		11		5
CERC Corp [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Revenues															1		0		1
Depreciation and Amortization															0		0		0
Operating Income (Loss)															3		(7)		(1)
Expenditures for Long-Lived Assets															0		0		0
CERC Corp [Member] | Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Total Assets		6,956	[6]				6,608								6,956	[6]	6,608		6,099
CERC Corp [Member] | Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Total Assets		1,558	[6]				1,521								1,558	[6]	1,521		1,102
CERC Corp [Member] | Operating Segments [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Total Assets		66	[6]				70								66	[6]	70		75
CERC Corp [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues															(146)		(85)		(55)
Total Assets		$ (366)	[6]				(559)								(366)	[6]	(559)		(563)
CERC Corp [Member] | Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues															(36)		(33)		(29)
CERC Corp [Member] | Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues															(110)		(52)		(26)
CERC Corp [Member] | Intersegment Eliminations [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Revenues															0		0		0
CERC Corp [Member] | Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Expenditures for Long-Lived Assets															$ (25)		(21)		2
Enable Midstream Partners [Member] | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | CERC Corp [Member]
Segment Reporting Information [Line Items]
Revenues																	0		0
Depreciation and Amortization																	0		0
Operating Income (Loss)																	0		0
Investment in unconsolidated affiliates - discontinued operations							$ 2,472	[6]									2,472	[6]	2,505	[6]	$ 2,400
Expenditures for Long-Lived Assets																	$ 0		$ 0

[1] Recast to reflect the adoption of ASU 2017-07. See Note 2(r) for further information.

[2] Represents amounts billed under the Transition Agreements for certain support services provided to Enable. Actual transition services costs are recorded net of reimbursement.

[3] CenterPoint Energy’s and Houston Electric’s Electric Transmission & Distribution revenues from major customers are as follows: Year Ended December 31, 2018 2017 2016 (in millions)Affiliates of NRG $705 $713 $698Affiliates of Vistra Energy Corp. 251 229 220

[4] CenterPoint Energy’s Midstream Investments’ equity earnings, net are as follows: Year Ended December 31, 2018 2017 2016 (in millions)Enable $307 $265 $208

[5] Total assets included pension and other postemployment-related regulatory assets of $665 million, $600 million and $759 million as of December 31, 2018, 2017 and 2016, respectively. Additionally, total assets as of December 31, 2018 included $3.9 billion of temporary investments included in Cash and cash equivalents on CenterPoint Energy’s Consolidated Balance Sheets.

[6] On September 4, 2018, CERC completed the Internal Spin. For further information regarding the Internal Spin, see Note 11.