Unconsolidated Affiliates (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		12 Months Ended
		Apr. 16, 2014	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2015	May. 30, 2014	Mar. 31, 2014	May. 01, 2013
Accounts and notes receivable — affiliated companies			$ 8		$ 8	$ 18
Service Agreement Notice For Termination At Term End					90 days
Equity Method Investment, Contributed Ownership Percentage											24.95%
Basis Difference, Amortization Period					33 years
Equity in earnings (losses) of unconsolidated affiliates					$ (1,633)	308	$ 188
Investment in unconsolidated affiliates			2,594		2,594	4,521
Summarized unaudited consolidated balance sheet from Enable [Abstract]
Investment in unconsolidated affiliates			2,594		2,594	4,521
Distribution received from unconsolidated affiliates [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions					294	305	129
Southeast Supply Header LLC [Member]
Equity Method Investment, Ownership Percentage										25.05%
Equity Method Investment, Contributed Ownership Percentage								0.10%	24.95%
Equity in earnings (losses) of unconsolidated affiliates	[1]				0	5	15
Investment in unconsolidated affiliates	[2]		0		0	1
Summarized unaudited consolidated balance sheet from Enable [Abstract]
Investment in unconsolidated affiliates	[2]		$ 0		0	1
Distribution received from unconsolidated affiliates [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions	[1]				$ 0	7	23
Enable Midstream Partners [Member]
Partners' Capital Account, Units, Sold in Public Offering		28,750,000
Share Price		$ 20.00
Proceeds from Issuance Initial Public Offering		$ 464
Equity Method Investment, Ownership Percentage			55.40%		55.40%				54.70%	58.30%
Equity in earnings (losses) of unconsolidated affiliates					$ (1,633)	303	173
Impairment Charges			$ 984	$ 862
Equity Method Investment, Other than Temporary Impairment			975	250	1,225	0	0
Goodwill And Long-LIved Assets Impairment Charges, Entity's Share					621
Investment in unconsolidated affiliates			2,594		2,594	4,520
Summarized unaudited consolidated income from Enable [Abstract]
Operating revenues					2,418	3,367	2,123
Cost of sales, excluding depreciation and amortization					1,097	1,914	1,241
Impairment of goodwill and other long-lived assets					1,134	8	12
Operating income (loss)					(712)	586	322
Net income (loss) attributable to Enable					(752)	530	289
Equity Method Investment, Gross Equity In Earnings (Losses)					(416)	298	168
Basis difference amortization (1)	[3]				8	5	5
Equity Method Investment, Other than Temporary Impairment			(975)	$ (250)	(1,225)	0	0
CERC’s equity in earnings (losses), net (2)	[4]				(1,633)	303	173
Income (Loss) From Equity Method Investment, Excluding Impairment Charge					213
Summarized unaudited consolidated balance sheet from Enable [Abstract]
Current assets			381		381	438
Non-current assets			10,857		10,857	11,399
Current liabilities			615		615	671
Non-current liabilities			3,092		3,092	2,343
Non-controlling interest			12		12	31
Enable partners’ capital			7,519		7,519	8,792
CERC’s ownership interest in Enable partners’ capital			4,163		4,163	4,869
CERC’s basis difference			(1,569)		(1,569)	(349)
Investment in unconsolidated affiliates			2,594		2,594	4,520
Distribution received from unconsolidated affiliates [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions					294	298	$ 106
Enable Midstream Partners [Member] | ArcLight [Member]
Partners' Capital Account, Units, Sold in Public Offering		3,750,000
Enable Midstream Partners [Member] | CERC Corp [Member]
Impairment Charges					1,846
Enable Guaranteed Senior Notes [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted			1,100		1,100
Enable Midstream Partners [Member]
Notes receivable — affiliated companies			363		$ 363
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum					2.10%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum					2.45%
Interest Income, Related Party					$ 8	8
Accounts and notes receivable — affiliated companies			4		4	4
Enable Midstream Partners [Member] | Enable Guaranteed Senior Notes [Member]
Guarantor Obligations, Maximum Exposure, Undiscounted			1,100		1,100
Transitional Service [Member] | Enable Midstream Partners [Member]
Reimbursement Revenue					16	163
Accounts Receivable, Related Parties			$ 3		$ 3	28
Common Stock [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Ownership, Shares			94,151,707		94,151,707
Subordinated Units [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Ownership, Shares			139,704,916		139,704,916
Natural Gas Expenses [Member] | Enable Midstream Partners [Member]
Affiliate Costs					$ 117	130
Accounts Payable, Related Parties, Current			$ 11		$ 11	$ 23
Enable Midstream Partners [Member]
Management Rights Ownership Percentage					50.00%
Enable Midstream Partners [Member] | OGE [Member]
Management Rights Ownership Percentage					50.00%
Incentive Distribution Right, Percentage					60.00%
Enable Midstream Partners [Member] | CERC Corp [Member]
Management Rights Ownership Percentage					50.00%
Incentive Distribution Right, Percentage					40.00%

[1] 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.

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

[3] 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.

[4] 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.