Derivative Financial Instruments By Income Statement Location (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Designated As Cash Flow And Fair Value Hedges
Interest rate swaps - ineffectiveness recorded as an offset to interest expense	$ 2		$ 0		$ 2		$ 0
Footnotes to Derivative Instruments by Income Statement Location [Abstract]
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	2				2
Weather Derivative	4				4
Natural gas contracts
Designated As Cash Flow And Fair Value Hedges
Cash Flow Hedge Gain (Loss) Reclassified to Cost of Sales, Net	(1)	[1]	(3)	[1]	(2)	[1]	(13)	[1]
Not Designated As Hedges
Fair Value adjustments recorded in Operating Revenues	0	[2]	40	[2]	12	[2]	63	[2]
Derivative Instruments Gain Loss By Hedging Net Fair Value Adjustments Recorded In Cost Gas	0	[3]	(1)	[3]	(2)	[3]	(3)	[3]
Total gains on derivative instruments	1		36		10		47
Footnotes to Derivative Instruments by Income Statement Location [Abstract]
Weather Derivative			$ 21				$ 21

[1] We expect that $2 million of pre-tax net losses will be reclassified from OCI into cost of gas for the settlement of hedged items over the next twelve months.

[2] Associated with the fair value of existing derivative instruments at September 30, 2011 and 2010.

[3] Excludes losses recorded in cost of gas associated with weather derivatives of $4 million for the nine months ended September 30, 2011 and losses of $21 million for the nine months ended September 30, 2010.