Reportable Business Segments (Details) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenue from External Customers		$ 1,349	$ 978	$ 807	$ 1,320	$ 1,087	[1]	$ 799	[2]	$ 824	$ 1,817	$ 4,454	$ 4,527	$ 6,367
Depreciation and Amortization												249	227	206
Operating Income (Loss)		108	$ 26	$ 18	$ 166	108	[1]	18	[2]	$ 27	$ 160	318	313	335
Assets	[3]	9,218				9,141						9,218	9,141	11,030
Capital Expenditures for Long-Lived Assets												515	606	528
Equity income												208	(1,633)	308
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												2,380	2,603	3,271
Depreciation and Amortization												242	222	201
Operating Income (Loss)												303	273	287
Capital Expenditures for Long-Lived Assets												510	601	525
Energy Services [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												2,073	1,924	3,095
Depreciation and Amortization												7	5	5
Operating Income (Loss)												20	42	52
Capital Expenditures for Long-Lived Assets												5	5	3
Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	[4]											0	0	0
Depreciation and Amortization	[4]											0	0	0
Operating Income (Loss)	[4]											0	0	0
Capital Expenditures for Long-Lived Assets	[4]											0	0	0
Equity income												208	(1,633)	308
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												1	0	1
Depreciation and Amortization												0	0	0
Operating Income (Loss)												(5)	(2)	(4)
Capital Expenditures for Long-Lived Assets												0	0	0
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Assets	[3]	6,099				5,657						6,099	5,657	5,464
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Assets	[3]	1,102				857						1,102	857	978
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Assets	[3],[4]	2,505				2,594						2,505	2,594	4,521
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets	[3]	75				777						75	777	1,031
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												(55)	(62)	(114)
Assets	[3]	$ (563)				(744)						(563)	(744)	(964)
Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												(29)	(29)	(30)
Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers												(26)	(33)	(84)
Intersegment Eliminations [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	[4]											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	[5]											208	(1,633)	303
Impairment Charges						$ 984		$ 862					1,846
Equity Method Investment, Other than Temporary Impairment												0	1,225	0
Goodwill And Long-LIved Assets Impairment Charges, Entity's Share													621
Income (Loss) From Equity Method Investment, Excluding Impairment Charge													213
Enable Midstream Partners [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Equity income	[6]											208	(1,633)	303
Southeast Supply Header LLC [Member]
Segment Reporting Information [Line Items]
Equity income	[7]											0	0	5
Southeast Supply Header LLC [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Equity income												$ 0	$ 0	$ 5

[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] Amounts for 2015 and 2014 have been restated to reflect the adoption of ASU 2015-03.

[4] Midstream Investments’ equity earnings (losses) are as follows: Year Ended December 31, 2016 2015 2014 (in millions)Enable (a) $208 $(1,633) $303SESH — — 5 Total $208 $(1,633) $308(a)These amounts include impairment charges totaling $1,846 million composed of CERC’s impairment of its equity method investment in Enable of $1,225 million and CERC’s share, $621 million, of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.

[5] These amounts include impairment charges totaling $1,846 million composed of CERC’s impairment of its equity method investment in Enable of $1,225 million and CERC’s share, $621 million, of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.

[6] These amounts include impairment charges totaling $1,846 million composed of CERC’s impairment of its equity method investment in Enable of $1,225 million and CERC’s share, $621 million, of impairment charges Enable recorded for goodwill and long-lived assets for 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 0.1% interest in SESH to Enable on June 30, 2015.