Asset Retirement Obligations (Changes to AROs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
AROs, Beginning balance	$ 1,591	[1]	$ 1,614	[1]
Obligations incurred during the period	16		1
Obligations settled during the period	(16)		(9)
Revisions in estimated cash flows	(277)	[2]	5
Accretion	84		85
Obligations relieved due to sale of Appalachian E&P operations			(105)
AROs , Ending balance	1,398	[1]	1,591	[1]
Other current liabilities	$ 15		$ 14		$ 9

[1] Includes $9 million, $14 million and $15 million reported in other current liabilities at December 31, 2009, 2010, and 2011, respectively.

[2] Primarily reflects the effect of lower anticipated costs due to the expected future recovery from the DOE of certain spent fuel storage costs.