Unconsolidated Affiliates (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		12 Months Ended
		Nov. 22, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2015	May 30, 2014	Dec. 31, 2013
Service Agreement Notice For Termination At Term End					90 days
Service Agreement Notice For Termination At Will Number Of Days					180 days
Transaction with Enable [Abstract]
Interest receivable related to notes receivable from Enable			$ 8		$ 5		$ 8
Investment in unconsolidated affiliates			2,594		2,505		2,594
Equity in earnings (losses) of unconsolidated affiliates					$ 208		(1,633)	$ 308
Limited Partner Interest in Enable [Abstract]
Sale of Units, Percentage, Trigger Right of First Refusal					5.00%
Summarized unaudited consolidated income from Enable [Abstract]
Basis Difference, Amortization Period					33 years
Summarized unaudited consolidated balance sheet from Enable [Abstract]
Investment in unconsolidated affiliates			$ 2,594		$ 2,505		2,594
Distribution received from unconsolidated affiliates [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions					$ 297		294	305
OGE [Member]
Limited Partner Interest in Enable [Abstract]
Sale of Units, Percentage, Trigger Right of First Refusal					5.00%
Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Share Price					$ 15.73
Southeast Supply Header LLC [Member]
Equity Method Investment, Ownership Percentage											25.05%
Transaction with Enable [Abstract]
Equity in earnings (losses) of unconsolidated affiliates	[1]				$ 0		0	5
Equity Method Investment, Contributed Ownership Percentage									0.10%	24.95%
Limited Partner Interest in Enable [Abstract]
Equity Method Investment, Ownership Percentage											25.05%
Distribution received from unconsolidated affiliates [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions	[1]				$ 0		$ 0	$ 7
Enable Midstream Partners [Member]
Equity Method Investment, Ownership Percentage			55.40%		54.10%	[2]	55.40%	55.40%
Transaction with Enable [Abstract]
Equity Method Investment, Other than Temporary Impairment					$ 0		$ 1,225	$ 0
Equity Method Investment, Carrying Value Per Unit					$ 10.71
Investment in unconsolidated affiliates			$ 2,594		$ 2,505		2,594
Equity in earnings (losses) of unconsolidated affiliates	[3]				$ 208		$ (1,633)	$ 303
Limited Partner Interest in Enable [Abstract]
Equity Method Investment, Ownership Percentage			55.40%		54.10%	[2]	55.40%	55.40%
Partners' Capital Account, Units, Sold in Public Offering		10,000,000
Summarized unaudited consolidated income from Enable [Abstract]
Operating revenues					$ 2,272		$ 2,418	$ 3,367
Cost of sales, excluding depreciation and amortization					1,017		1,097	1,914
Impairment of goodwill and other long-lived assets					9		1,134	8
Operating income (loss)					385		(712)	586
Net income (loss) attributable to Enable					290		(752)	530
CERC’s interest					160		(416)	298
Basis difference amortization (1)	[4]				48		8	5
Impairment of CERC’s equity method investment in Enable					0		(1,225)	0
Impairment Charges			$ 984	$ 862			1,846
Goodwill And Long-LIved Assets Impairment Charges, Entity's Share							621
Income (Loss) From Equity Method Investment, Excluding Impairment Charge							213
Summarized unaudited consolidated balance sheet from Enable [Abstract]
Current assets			381		396		381
Non-current assets			10,845		10,816		10,845
Current liabilities			615		362		615
Non-current liabilities			3,080		3,056		3,080
Non-controlling interest			12		12		12
Preferred equity			0		362		0
Enable partners’ capital			7,519		7,420		7,519
CERC’s ownership interest in Enable partners’ capital			4,163		4,067		4,163
CERC’s basis difference			(1,569)		(1,562)		(1,569)
Investment in unconsolidated affiliates			2,594		2,505		2,594
Distribution received from unconsolidated affiliates [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions					297		294	298
Enable Midstream Partners [Member] | ArcLight [Member]
Limited Partner Interest in Enable [Abstract]
Partners' Capital Account, Units, Sold in Public Offering		1,500,000
Enable Midstream Partners [Member]
Extinguishment of Debt, Amount					363
Transaction with Enable [Abstract]
Interest income related to notes receivable from Enable					1		8	8
Interest receivable related to notes receivable from Enable			4		0		4
Transitional Service [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Reimbursement of transition services (1)	[5]				7		16	163
Accounts receivable for amounts billed for transition services			3		$ 1		3
Common Stock [Member] | Enable Midstream Partners [Member]
Limited Partner Interest in Enable [Abstract]
Equity Method Investment, Ownership, Shares					94,151,707
Subordinated Units [Member] | Enable Midstream Partners [Member]
Limited Partner Interest in Enable [Abstract]
Equity Method Investment, Ownership, Shares					139,704,916
Natural Gas Expenses [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Natural gas expenses, including transportation and storage costs					$ 110		117	$ 130
Accounts payable for natural gas purchases from Enable			11		$ 10		$ 11
Enable Midstream Partners [Member]
Limited Partner Interest in Enable [Abstract]
Management Rights Ownership Percentage					50.00%
Distribution received from unconsolidated affiliates [Abstract]
Incentive Distribution Right					40.00%
Incentive Distribution Right, Maximum					50.00%
Enable Midstream Partners [Member] | OGE [Member]
Limited Partner Interest in Enable [Abstract]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage					25.70%		26.30%	26.30%
Management Rights Ownership Percentage					50.00%
Distribution received from unconsolidated affiliates [Abstract]
Incentive Distribution Right					60.00%
Enable Midstream Partners [Member] | Common Stock [Member] | OGE [Member]
Limited Partner Interest in Enable [Abstract]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership, Shares					42,832,291
Enable Midstream Partners [Member] | Subordinated Units [Member] | OGE [Member]
Limited Partner Interest in Enable [Abstract]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership, Shares					68,150,514
Minimum [Member] | Enable Midstream Partners [Member]
Debt Instrument, Interest Rate, Stated Percentage Rate Range					2.10%
Minimum [Member] | Enable Midstream Partners [Member]
Distribution received from unconsolidated affiliates [Abstract]
Incentive Distribution, Distribution Per Unit					$ 0.2875
Maximum [Member] | Enable Midstream Partners [Member]
Debt Instrument, Interest Rate, Stated Percentage Rate Range					2.45%
Maximum [Member] | Enable Midstream Partners [Member]
Distribution received from unconsolidated affiliates [Abstract]
Incentive Distribution, Distribution Per Unit					$ 0.330625
Midstream Investments [Member]
Transaction with Enable [Abstract]
Equity in earnings (losses) of unconsolidated affiliates					$ 208		$ (1,633)	$ 308
Midstream Investments [Member] | Southeast Supply Header LLC [Member]
Transaction with Enable [Abstract]
Equity in earnings (losses) of unconsolidated affiliates					0		0	5
Midstream Investments [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Investment in unconsolidated affiliates			2,594		2,505		2,594
Equity in earnings (losses) of unconsolidated affiliates	[6]				208		(1,633)	$ 303
Summarized unaudited consolidated balance sheet from Enable [Abstract]
Investment in unconsolidated affiliates			$ 2,594		$ 2,505		$ 2,594

[1] 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.

[2] In November 2016, Enable closed a public offering of 10,000,000 common units. In connection with the offering, Enable and an affiliate of ArcLight sold an additional combined 1,500,000 common units to the underwriters.

[3] 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.

[4] Equity in earnings of unconsolidated affiliates includes CERC’s share of Enable earnings adjusted for the amortization of the basis difference of CERC’s original investment in Enable and its underlying equity in net assets of Enable. The basis difference is being amortized over approximately 33 years, the average life of the assets to which the basis difference is attributed.

[5] Represents amounts billed under the Transition Agreements, including the costs of seconded employees. Actual transition services costs are recorded net of reimbursement.

[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.