v2.4.0.6
Variable Interest Entities and Unconsolidated Investments (Unconsolidated Investements) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Income Loss from Unconsolidated Investments in Power Plants and Distributions [Line Items]      
(Income) loss from unconsolidated investments in power plants $ (21) $ (16) $ (50)
Return on investment in unconsolidated subsidiaries 6 11 20
OMEC [Member]
      
Income Loss from Unconsolidated Investments in Power Plants and Distributions [Line Items]      
(Income) loss from unconsolidated investments in power plants 0 [1] 0 [1] (32) [1]
Return on investment in unconsolidated subsidiaries 0 [1] 0 [1] 9 [1]
Greenfield [Member]
      
Income Loss from Unconsolidated Investments in Power Plants and Distributions [Line Items]      
(Income) loss from unconsolidated investments in power plants (12) (8) (16)
Return on investment in unconsolidated subsidiaries 2 6 9
Whitby [Member]
      
Income Loss from Unconsolidated Investments in Power Plants and Distributions [Line Items]      
(Income) loss from unconsolidated investments in power plants (9) (8) (2)
Return on investment in unconsolidated subsidiaries $ 4 $ 5 $ 2
[1] OMEC was consolidated effective January 1, 2010. See Note 2.