Dispositions (Schedule of Disposal Groups, Including Discontinued Operations, Income Statement) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge	$ 2,100
State Line and Salem Harbor
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenue	57		233		269
Loss before income taxes	(49)	[1]	(34)	[1]	(158)	[1]
Impairment charge			55		194
Peoples
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenue					67
Loss before income taxes					$ (134)	[2]

[1] Includes long-lived asset impairment charges of $55 million and $194 million in 2011 and 2010, respectively.

[2] Includes a loss and other charges related to the sale of Peoples.