Unconsolidated Affiliate (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		9 Months Ended
		Nov. 22, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Aug. 30, 2017	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 Corp.’s equity in earnings, net			$ 68	$ 73	$ 199	$ 164
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CERC Corp.’s equity method investment in Enable			$ 2,481		$ 2,481			$ 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			$ 705	620	$ 1,997	1,658
Cost of sales, excluding depreciation and amortization			349	268	936	717
Impairment of goodwill and other long-lived assets			0	8	0	8
Operating income			137	139	399	299
Net income attributable to Enable			104	110	301	231
CERC Corp.’s interest			56	61	163	128
Basis difference amortization (1)	[1]		12	12	36	36
CERC Corp.’s equity in earnings, net			68	73	$ 199	164
Basis difference amortization period					33 years
Equity Method Investment, Summarized Financial Information, Assets and Liabilities [Abstract]
Current assets			446		$ 446			396
Non-current assets			10,816		10,816			10,816
Current liabilities			831		831			362
Non-current liabilities			2,740		2,740			3,056
Non-controlling interest			12		12			12
Preferred equity			362		362			362
Enable partners’ capital			7,317		7,317			7,420
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CERC’s ownership interest in Enable partners’ capital			4,007		4,007			4,067
CERC Corp.’s basis difference			(1,526)		(1,526)			(1,562)
CERC Corp.’s equity method investment in Enable			2,481		2,481			2,505
Distributions received from equity method investment			74	74	$ 223	223
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			23	22	$ 80	79
Accounts payable for natural gas purchases from Enable			8		8			10
Transitional Service [Member] | Enable Midstream Partners [Member]
Reimbursement of transition services (1)	[2]		0	$ 1	3	$ 6
Accounts receivable for amounts billed for transition services			$ 1		$ 1			$ 1
Common Stock [Member] | Enable Midstream Partners [Member]
Enable equity method investment units held			233,856,623		233,856,623
Common Stock [Member] | Enable Midstream Partners [Member] | OGE [Member]
Enable units held					110,982,805
Subordinated Units [Member] | Enable Midstream Partners [Member]
Enable equity method investment units held							139,704,916

[1] Equity in earnings of unconsolidated affiliates includes CERC Corp.’s share of Enable’s earnings adjusted for the amortization of the basis difference of CERC Corp.’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.