Reportable Business Segments (Details) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenue from External Customers		$ 1,087	[1]	$ 799	[2]	$ 824	$ 1,817	$ 1,689	$ 964	$ 1,183	$ 2,531	$ 4,527	$ 6,367	$ 5,522
Depreciation and Amortization												227	206	230
Operating Income (Loss)		108	[1]	18	[2]	$ 27	$ 160	111	$ (3)	$ 39	$ 188	313	335	401
Assets		9,153						11,044				9,153	11,044	10,532
Capital Expenditures for Long-Lived Assets												606	528	478
Equity income												(1,633)	308	188
Investment in unconsolidated affiliate		2,594						4,521				2,594	4,521
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												2,603	3,271	2,837
Depreciation and Amortization												222	201	185
Operating Income (Loss)												273	287	263
Capital Expenditures for Long-Lived Assets												601	525	430
Energy Services [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												1,924	3,095	2,374
Depreciation and Amortization												5	5	5
Operating Income (Loss)												42	52	13
Capital Expenditures for Long-Lived Assets												5	3	3
Interstate Pipelines [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	[3],[4]													133
Depreciation and Amortization	[3],[4]													20
Operating Income (Loss)	[3],[4]													72
Capital Expenditures for Long-Lived Assets	[3],[4]													29
Field Services [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	[4]													178
Depreciation and Amortization	[4]													20
Operating Income (Loss)	[4]													73
Capital Expenditures for Long-Lived Assets	[4]													16
Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	[5]											0	0	0
Depreciation and Amortization	[5]											0	0	0
Operating Income (Loss)	[5]											0	0	0
Capital Expenditures for Long-Lived Assets	[5]											0	0	0
Equity income												(1,633)	308	181
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												0	1	0
Depreciation and Amortization												0	0	0
Operating Income (Loss)												(2)	(4)	(20)
Capital Expenditures for Long-Lived Assets												0	0	0
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Assets		5,657						5,464				5,657	5,464	4,976
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Assets		857						978				857	978	895
Operating Segments [Member] | Interstate Pipelines [Member]
Segment Reporting Information [Line Items]
Assets	[3],[4]													0
Operating Segments [Member] | Field Services [Member]
Segment Reporting Information [Line Items]
Assets	[4]													0
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Assets	[5]	2,594						4,521				2,594	4,521	4,518
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets		789						1,045				789	1,045	1,139
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												(62)	(114)	(124)
Assets		(744)						(964)				(744)	(964)	(996)
Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												(29)	(30)	(26)
Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												(33)	(84)	(27)
Intersegment Eliminations [Member] | Interstate Pipelines [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	[3],[4]													(53)
Intersegment Eliminations [Member] | Field Services [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	[4]													(18)
Intersegment Eliminations [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	[5]											0	0	0
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												0	0	0
Enable Midstream Partners [Member]
Segment Reporting Information [Line Items]
Equity income												(1,633)	303	173
Impairment Charges		984		$ 862
Income (Loss) From Equity Method Investment, Excluding Impairment Charge												213
Investment in unconsolidated affiliate		2,594						4,520				2,594	4,520
Enable Midstream Partners [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Equity income	[6]											(1,633)	303	173
Enable Midstream Partners [Member] | CERC Corp [Member]
Segment Reporting Information [Line Items]
Impairment Charges												1,846
Southeast Supply Header LLC [Member]
Segment Reporting Information [Line Items]
Equity income	[7]											0	5	15
Investment in unconsolidated affiliate	[8]	$ 0						$ 1				0	1
Southeast Supply Header LLC [Member] | Interstate Pipelines [Member]
Segment Reporting Information [Line Items]
Equity income														7
Southeast Supply Header LLC [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Equity income												$ 0	$ 5	$ 8

[1] CERC recognized $984 million ($620 million after tax) in impairment charges related to Enable during the three months ended December 31, 2015.

[2] CERC recognized $862 million ($537 million after tax) in impairment charges related to Enable during the three months ended September 30, 2015.

[3] Interstate Pipelines recorded equity income of $7 million in the year ended December 31, 2013 from its interest in SESH, a jointly-owned pipeline. These amounts are included in Equity in earnings of unconsolidated affiliates under the Other Income (Expense) caption. As discussed above, effective May 1, 2013, CenterPoint Energy reports equity earnings associated with its interest in Enable and equity earnings associated with its interest in SESH under its Midstream Investments segment, and no longer has an Interstate Pipelines reporting segment prospectively.

[4] Results reflected in the year ended December 31, 2013 represent only January 2013 through April 2013.

[5] Midstream Investments’ equity earnings (losses) are as follows: Year Ended December 31, 2015 2014 2013 (in millions)Enable (1) $(1,633) $303 $173SESH — 5 8 Total $(1,633) $308 $181(1)These amounts include CERC’s share of Enable’s impairment of goodwill and long-lived assets and the impairment of CERC’s equity method investment in Enable totaling $1,846 million during the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.Midstream Investments’ total assets are as follows: December 31, 2015 December 31, 2014 (in millions)Enable $2,594 $4,520SESH — 1 Total $2,594 $4,521

[6] These amounts include CERC’s share of Enable’s impairment of goodwill and long-lived assets and the impairment of CERC’s equity method investment in Enable totaling $1,846 million during the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.

[7] CERC contributed a 24.95% interest in SESH to Enable on May 30, 2014 and its remaining interest in SESH to Enable on June 30, 2015.

[8] CERC disposed of its remaining interest in SESH on June 30, 2015.