Variable Interest Entities and Unconsolidated Investments (Income from Unconsolidated Investements 10-Q) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
(Income) loss from unconsolidated investments in power plants	$ (5)	$ 2	$ (14)	$ (7)
Greenfield [Member]
(Income) loss from unconsolidated investments in power plants	(2)	4	(8)	(1)
Whitby [Member]
(Income) loss from unconsolidated investments in power plants	$ (3)	$ (2)	$ (6)	$ (6)