Unconsolidated Affiliate Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
CERC’s equity in earnings, net		$ 72	$ 60
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CERC’s equity method investment in Enable		2,502		$ 2,505
Enable Midstream Partners [Member]
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Operating revenues		666	509
Cost of sales, excluding depreciation and amortization		308	195
Operating income		140	103
Net income attributable to Enable		111	86
CERC’s interest		60	48
Basis difference amortization (1)	[1]	12	12
CERC’s equity in earnings, net		$ 72	60
Basis Difference, Amortization Period		33 years
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Current assets		$ 375		396
Non-current assets		10,786		10,816
Current liabilities		279		362
Non-current liabilities		3,111		3,056
Non-controlling interest		12		12
Preferred equity		362		362
Enable partners’ capital		7,397		7,420
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CERC’s ownership interest in Enable partners’ capital		4,053		4,067
CERC’s basis difference		(1,551)		(1,562)
CERC’s equity method investment in Enable		2,502		$ 2,505
Proceeds from Equity Method Investment, Dividends or Distributions		$ 74	$ 74
Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive Distribution Right		40.00%
Incentive Distribution Right, Maximum		50.00%
Enable Midstream Partners [Member] | OGE [Member]
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, Distribution Per Unit		$ 0.2875
Maximum [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive Distribution, Distribution Per Unit		$ 0.330625

[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.