Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Collateral Posted with Same Counterparties	$ (1)
ASSETS
Corporate equities	2				2
Investments, including money market funds	11				11
Natural gas derivatives, gross asset	41				43
Natural gas derivatives, assets	33				34	[1]
Total assets	46				47
Liabilities [Abstract]
natural gas derivatives, gross liabilities	26				30
Natural gas derivatives, liabilities	19				21
Total liabilities	19				21
Cash collateral posted with counterparties					1
Derivative Instruments, Assets, Physical Forwards Purchased					1
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Beginning balance	3		2
Total gains (losses)	(2)		2
Total settlements	1		(1)
Transfers into Level 3	(1)		0
Ending balance (1)	1	[2]	3	[2]
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at the reporting date	(2)		2
Carrying Amount [Member]
Liabilities [Abstract]
Notes receivable from unconsolidated affiliates	363				363
Long-term debt	2,124				2,240
Fair Value [Member]
Liabilities [Abstract]
Notes receivable from unconsolidated affiliates	365				363
Long-term debt	2,399				2,466
Fair Value, Inputs, Level 1 [Member]
ASSETS
Corporate equities	2				2
Investments, including money market funds	11				11
Natural gas derivatives, gross asset	4				5	[1]
Total assets	17				18
Liabilities [Abstract]
natural gas derivatives, gross liabilities	1				1
Total liabilities	1				1
Fair Value, Inputs, Level 2 [Member]
ASSETS
Corporate equities	0				0
Investments, including money market funds	0				0
Natural gas derivatives, gross asset	32				33	[1]
Total assets	32				33
Liabilities [Abstract]
natural gas derivatives, gross liabilities	20				27
Total liabilities	20				27
Fair Value, Inputs, Level 3 [Member]
ASSETS
Corporate equities	0				0
Investments, including money market funds	0				0
Natural gas derivatives, gross asset	5				5	[1]
Total assets	5				5
Liabilities [Abstract]
natural gas derivatives, gross liabilities	5				2
Total liabilities	5				2
Netting [Member]
ASSETS
Corporate equities	0	[3]			0	[4]
Investments, including money market funds	0	[3]			0	[4]
Natural gas derivatives, netting adjustment	(8)	[3]			(9)	[1],[4]
Liabilities [Abstract]
Natural gas derivatives, netting adjustment	$ (7)	[3]			$ (9)	[4]
Minimum [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Option volatilities	0.00%
Maximum [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Option volatilities	62.00%
Forward Contracts [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Illiquid forward price low range	3.43
Forward Contracts [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Illiquid forward price low range	5.20

[1] The (Level 2) Natural gas derivative assets of $33 million includes $1 million related to physical forwards purchased from Enable.

[2] CERC did not have significant Level 3 purchases, sales or transfers out of Level 3 during the three months ended March 31, 2014 or 2013.

[3] Amounts represent the impact of legally enforceable master netting arrangements that allow CERC to settle positive and negative positions and also include cash collateral of $(1) million posted with the same counterparties.

[4] Amounts represent the impact of legally enforceable master netting arrangements that allow CERC to settle positive and negative positions and also include cash collateral of less than $1 million posted with the same counterparties.