Fair Value Measurements (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Assets
Corporate equities	$ 2,000,000		$ 1,000,000
Investments, including money market funds	11,000,000		11,000,000
Natural gas derivatives (2)	34,000,000	[1]	42,000,000
Total assets	47,000,000		54,000,000
Liabilities
Natural gas derivatives	21,000,000		16,000,000
Total liabilities	21,000,000		16,000,000
Cash collateral posted with counterparties	1,000,000		9,000,000
Derivative Instruments, Assets, Physical Forwards Purchased	1,000,000
Carrying Amount [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Notes receivable - affiliated companies	363,000,000		0
Long-term debt	2,240,000,000		2,641,000,000
Fair Value [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Notes receivable - affiliated companies	363,000,000		0
Long-term debt	2,466,000,000		3,094,000,000
Derivative Financial Instruments Assets And Liabilities Net Member
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Beginning balance	2,000,000	[2]	6,000,000	[2]	3,000,000
Total gains (1)	3,000,000	[3]	3,000,000	[3]	6,000,000	[3]
Total settlements (1)	(3,000,000)	[3]	(6,000,000)	[3]	(3,000,000)	[3]
Total purchases	0		0		2,000,000
Transfers out of Level 3	0		(1,000,000)		(2,000,000)
Transfers into Level 3	1,000,000		0		0
Ending balance (2)	3,000,000	[2]	2,000,000	[2]	6,000,000	[2]
The amount of total gains for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at the reporting date	2,000,000		1,000,000		5,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets
Corporate equities	2,000,000		1,000,000
Investments, including money market funds	11,000,000		11,000,000
Natural gas derivatives (2)	5,000,000	[1]	1,000,000
Total assets	18,000,000		13,000,000
Liabilities
Natural gas derivatives	1,000,000		5,000,000
Total liabilities	1,000,000		5,000,000
Significant Other Observable Inputs (Level 2) [Member]
Assets
Corporate equities	0		0
Investments, including money market funds	0		0
Natural gas derivatives (2)	33,000,000	[1]	40,000,000
Total assets	33,000,000		40,000,000
Liabilities
Natural gas derivatives	27,000,000		21,000,000
Total liabilities	27,000,000		21,000,000
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Illiquid forward price low range	3.79
Illiquid forward price high range	4.94
Option volatilities low range	0.00%
Option volatilities high range	53.00%
Assets
Corporate equities	0		0
Investments, including money market funds	0		0
Natural gas derivatives (2)	5,000,000	[1]	7,000,000
Total assets	5,000,000		7,000,000
Liabilities
Natural gas derivatives	2,000,000		5,000,000
Total liabilities	2,000,000		5,000,000
Netting Adjustments [Member]
Assets
Corporate equities	0	[4]	0	[5]
Investments, including money market funds	0	[4]	0	[5]
Natural gas derivatives (2)	(9,000,000)	[1],[4]	(6,000,000)	[5]
Liabilities
Natural gas derivatives	$ (9,000,000)	[4]	$ (15,000,000)	[5]

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

[2] During 2013, 2012 and 2011, CERC did not have significant Level 3 sales.

[3] During 2013, 2012 and 2011, CERC did not have Level 3 unrealized gains (losses) or settlements related to price stabilization activities of the Natural Gas Distribution business segment.

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

[5] Amounts represent the impact of legally enforceable master netting agreements that allow CERC to settle positive and negative positions and also include cash collateral of $9 million posted with the same counterparties.