Reportable Business Segments (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2019		Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues		$ 2,742		$ 2,212	$ 9,071		$ 7,553
Operating Income (Loss)		392		226	924		664
Equity in earnings from investment in Enable		77		81	213		208
Assets		34,642			34,642			$ 27,009
Total regulatory assets		2,212			2,212			2,044
Houston Electric T&D [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	859		897	2,313		2,502
Operating Income (Loss)		269		227	522		523
Houston Electric T&D [Member] | Affiliates of NRG Energy, Inc. [Member]
Segment Reporting Information [Line Items]
Revenues		231		213	547		543
Houston Electric T&D [Member] | Affiliates of Vistra Energy Corp. [Member]
Segment Reporting Information [Line Items]
Revenues		83		79	196		192
Indiana Electric Integrated [Member]
Segment Reporting Information [Line Items]
Revenues		165		0	388		0
Operating Income (Loss)		48		0	64		0
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		515		402	2,554		2,032
Operating Income (Loss)		27		3	241		166
Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues		734		910	2,754		3,008
Operating Income (Loss)		2		(9)	64		(20)
Infrastructure Services [Member]
Segment Reporting Information [Line Items]
Revenues		376		0	847		0
Operating Income (Loss)		42		0	50		0
Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	0		0	0		0
Operating Income (Loss)	[2]	0		0	0		0
Equity in earnings from investment in Enable		77		81	213		208
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues		93		3	215		11
Operating Income (Loss)		4		5	(17)		(5)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(21)		(18)	(123)		(83)
Assets		(3,026)			(3,026)			(652)
Intersegment Eliminations [Member] | Houston Electric T&D [Member]
Segment Reporting Information [Line Items]
Revenues		0		0	0		0
Intersegment Eliminations [Member] | Indiana Electric Integrated [Member]
Segment Reporting Information [Line Items]
Revenues		0		0	0		0
Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		(9)		(8)	(29)		(26)
Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues		(11)		(10)	(92)		(57)
Intersegment Eliminations [Member] | Infrastructure Services [Member]
Segment Reporting Information [Line Items]
Revenues		(1)		0	(2)		0
Intersegment Eliminations [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	0		0	0		0
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues		0		0	0		0
Operating Segments [Member] | Houston Electric T&D [Member]
Segment Reporting Information [Line Items]
Assets		11,463			11,463			10,509
Operating Segments [Member] | Indiana Electric Integrated [Member]
Segment Reporting Information [Line Items]
Assets	[3]	3,009			3,009			0
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Assets		13,235	[3]		13,235	[3]		6,956
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Assets		1,264			1,264			1,558
Operating Segments [Member] | Infrastructure Services [Member]
Segment Reporting Information [Line Items]
Assets	[3]	1,284			1,284			0
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Assets		2,529			2,529			2,482
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets	[4]	4,884	[3]		4,884	[3]		6,156
Pension and Other Postretirement Plans Costs [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Total regulatory assets		625			625			665
Houston Electric [Member]
Segment Reporting Information [Line Items]
Revenues		859		897	2,310		2,506
Operating Income (Loss)		269		227	519		527
Assets		11,463			11,463			10,507
Total regulatory assets		951			951			1,124
Houston Electric [Member] | Houston Electric T&D [Member] | Affiliates of NRG Energy, Inc. [Member]
Segment Reporting Information [Line Items]
Revenues		231		213	547		543
Houston Electric [Member] | Houston Electric T&D [Member] | Affiliates of Vistra Energy Corp. [Member]
Segment Reporting Information [Line Items]
Revenues		83		79	196		192
CERC Corp [Member]
Segment Reporting Information [Line Items]
Revenues		1,126		1,312	4,836		5,040
Operating Income (Loss)		23		(7)	277		146
Assets		7,929			7,929			8,214
Total regulatory assets		207			207			258
CERC Corp [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		389		402	2,077		2,032
Operating Income (Loss)		20		3	212		166
CERC Corp [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues		734		910	2,755		3,008
Operating Income (Loss)		2		(9)	64		(20)
CERC Corp [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues		3		0	4		0
Operating Income (Loss)		1		(1)	1		0
CERC Corp [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(20)		(18)	(120)		(83)
Assets		(474)			(474)			(366)
CERC Corp [Member] | Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		(9)		(8)	(29)		(26)
CERC Corp [Member] | Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues		(11)		(10)	(91)		(57)
CERC Corp [Member] | Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues		0		$ 0	0		$ 0
CERC Corp [Member] | Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Assets		7,018			7,018			6,956
CERC Corp [Member] | Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Assets		1,264			1,264			1,558
CERC Corp [Member] | Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets	[3]	$ 121			$ 121			66
Cash and Cash Equivalents [Member]
Segment Reporting Information [Line Items]
Short-term Investments								$ 3,900

[1] Houston Electric T&D revenues from major external customers are as follows:     Three Months Ended September 30,   Nine Months Ended September 30,     2019   2018   2019   2018     (in millions) Affiliates of NRG   $ 231
  $ 213
  $ 547
  $ 543
Affiliates of Vistra Energy Corp.   83
  79
  196
  192

[2] CenterPoint Energy’s Midstream Investments’ equity in earnings, net are as follows:     Three Months Ended September 30,   Nine Months Ended September 30,     2019   2018   2019   2018     (in millions) Enable   $ 77
  $ 81
  $ 213
  $ 208

[3] Total assets by reportable segment include assets acquired in the Merger, which are based on preliminary fair value estimates and allocations on the acquisition date and are subject to change. See Note 3.

[4] Includes pension and other postemployment-related regulatory assets of $625 million and $665 million, respectively, as of September 30, 2019 and December 31, 2018. 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.