Reportable Business Segments (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues		$ 2,186	$ 2,143	$ 5,341	$ 4,878
Operating Income (Loss)		187	240	438	531
Equity in earnings from investment in Enable		58	59	127	131
Assets		22,108		22,108		$ 22,736
Total regulatory assets		2,122		2,122		2,477
Electric Transmission and Distribution [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	854	752	1,605	1,391
Operating Income (Loss)		181	171	296	257
Electric Transmission and Distribution [Member] | Affiliates of NRG Energy, Inc. [Member]
Segment Reporting Information [Line Items]
Revenues		169	167	330	319
Electric Transmission and Distribution [Member] | Affiliates of Vistra Energy Corp. [Member]
Segment Reporting Information [Line Items]
Revenues		59	53	113	100
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		487	470	1,630	1,377
Operating Income (Loss)		7	42	163	210
Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues		841	918	2,098	2,103
Operating Income (Loss)		15	16	(11)	51
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		58	59	127	131
Other Operations [Member]
Segment Reporting Information [Line Items]
Revenues		4	3	8	7
Operating Income (Loss)		(16)	11	(10)	13
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(27)	(20)	(65)	(40)
Assets		(841)		(841)		(654)
Intersegment Eliminations [Member] | Electric Transmission and Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		0	0	0	0
Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		(8)	(7)	(18)	(16)
Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues		(19)	(13)	(47)	(24)
Intersegment Eliminations [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	0	0	0	0
Intersegment Eliminations [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Revenues		0	0	0	0
Operating Segments [Member] | Electric Transmission and Distribution [Member]
Segment Reporting Information [Line Items]
Assets		10,430		10,430		10,292
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Assets		6,501		6,501		6,608
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Assets		1,256		1,256		1,521
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Assets		2,451		2,451		2,472
Operating Segments [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Assets	[3]	2,311		2,311		2,497
Pension and Other Postretirement Plans Costs [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Total regulatory assets		577		577		600
CERC Corp [Member]
Segment Reporting Information [Line Items]
Revenues		1,328	1,387	3,728	3,480
Operating Income (Loss)		22	59	153	258
Equity in earnings from investment in Enable		58	59	127	131
Assets		9,642		9,642		10,112
Total regulatory assets		228		228		311
CERC Corp [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		487	470	1,630	1,377
Operating Income (Loss)		7	42	163	210
CERC Corp [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues		841	918	2,098	2,103
Operating Income (Loss)		15	16	(11)	51
CERC Corp [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	0	0	0	0
Operating Income (Loss)	[2]	0	0	0	0
CERC Corp [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Revenues		0	(1)	0	0
Operating Income (Loss)		0	1	1	(3)
CERC Corp [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(27)	(20)	(65)	(40)
Assets		(655)		(655)		(559)
CERC Corp [Member] | Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues		(8)	(7)	(18)	(16)
CERC Corp [Member] | Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues		(19)	(13)	(47)	(24)
CERC Corp [Member] | Intersegment Eliminations [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	0	0	0	0
CERC Corp [Member] | Intersegment Eliminations [Member] | Other Operations [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		6,501		6,501		6,608
CERC Corp [Member] | Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Assets		1,256		1,256		1,521
CERC Corp [Member] | Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Assets		2,451		2,451		2,472
CERC Corp [Member] | Operating Segments [Member] | Other Operations [Member]
Segment Reporting Information [Line Items]
Assets		$ 89		$ 89		$ 70

[1] CenterPoint Energy’s and Houston Electric’s Electric Transmission & Distribution revenues from major customers are as follows:

[2] CenterPoint Energy’s and CERC’s Midstream Investments’ equity earnings, net are as follows: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 (in millions)Enable $58 $59 $127 $131

[3] Includes pension and other postemployment-related regulatory assets of $577 million and $600 million, respectively, as of June 30, 2018 and December 31, 2017.