Unconsolidated Affiliate (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		6 Months Ended
		Nov. 22, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Percentage sale of units which trigger right of first refusal					5.00%
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
CERC’s equity in earnings, net			$ 59	$ 31	$ 131	$ 91
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CERC’s equity method investment in Enable			$ 2,487		$ 2,487		$ 2,505
Enable Midstream Partners [Member]
Equity method investment limited partner interest in Enable			54.10%		54.10%
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Operating revenues			$ 626	529	$ 1,292	1,038
Cost of sales, excluding depreciation and amortization			279	254	587	449
Operating income			122	57	262	160
Net income attributable to Enable			86	35	197	121
CERC’s interest			47	19	107	67
Basis difference amortization (1)	[1]		12	12	24	24
CERC’s equity in earnings, net			59	31	$ 131	91
Basis difference amortization period					33 years
Equity Method Investment, Summarized Financial Information, Assets and Liabilities [Abstract]
Current assets			351		$ 351		396
Non-current assets			10,780		10,780		10,816
Current liabilities			298		298		362
Non-current liabilities			3,111		3,111		3,056
Non-controlling interest			12		12		12
Preferred equity			362		362		362
Enable partners’ capital			7,348		7,348		7,420
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CERC’s ownership interest in Enable partners’ capital			4,025		4,025		4,067
CERC’s basis difference			(1,538)		(1,538)		(1,562)
CERC’s equity method investment in Enable			2,487		2,487		2,505
Distributions received from equity method investment			75	75	$ 149	149
Enable and ArcLight [Member]
Units sold in public offering		1,424,281
OGE [Member]
Percentage sale of units which trigger right of first refusal					5.00%
Enable Midstream Partners [Member]
Units sold in public offering		11,500,000
Enable Midstream Partners [Member]
Interest income related to notes receivable from Enable			0	0	$ 0	1
Enable Midstream Partners [Member]
Management rights ownership percentage					50.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive distribution right					40.00%
Maximum incentive distribution right					50.00%
Enable Midstream Partners [Member] | OGE [Member]
Limited partner interest in Enable					25.70%
Management rights ownership percentage					50.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive distribution right					60.00%
Minimum [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive distribution per unit					$ 0.2875
Maximum [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive distribution per unit					$ 0.330625
Natural Gas Expenses [Member] | Enable Midstream Partners [Member]
Natural gas expenses, including transportation and storage costs			24	24	$ 57	57
Accounts payable for natural gas purchases from Enable			8		8		10
Transitional Service [Member] | Enable Midstream Partners [Member]
Reimbursement of transition services (1)	[2]		1	$ 2	3	$ 5
Accounts receivable for amounts billed for transition services			$ 1		$ 1		$ 1
Common Stock [Member] | Enable Midstream Partners [Member]
Enable equity method investment units held			94,151,707		94,151,707
Common Stock [Member] | Enable Midstream Partners [Member] | OGE [Member]
Enable units held					42,832,291
Subordinated Units [Member] | Enable Midstream Partners [Member]
Enable equity method investment units held			139,704,916		139,704,916
Subordinated Units [Member] | Enable Midstream Partners [Member] | OGE [Member]
Enable units held					68,150,514

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

[2] Represents amounts billed under the Transition Agreements for certain support services provided to Enable. Actual transition services costs are recorded net of reimbursement.