Variable Interest Entities And Unconsolidated Investments (Details 4) In Millions, unless otherwise specified	Jun. 30, 2011 USD ($)	Dec. 31, 2010 USD ($)	Jun. 30, 2011 Greenfield CAD	Jun. 30, 2011 Whitby	Jun. 30, 2011 Minimum Inland Empire Energy Center	Jun. 30, 2011 Maximum Inland Empire Energy Center	Jun. 30, 2011 Riverside Energy Center and OMEC	Jun. 30, 2011 Inland Empire Energy Center
Schedule of Equity Method Investments [Line Items]
Power generation capacity (in Megawatts)	11,064	13,553	1,038	50			1,211	775
Term loan years			18
Term loan amount			648
Project financing interest rate spread - Canadian LIBOR			1.125%
Project financing interest rate spread - Canadian Prime Rate			0.125%
Call option exercise years					7	14
Put option exercise year								15
Variable Interest Entities and Unconsolidated Investments (Textuals) [Abstract]
Equity method investee debt	514	494
Pro rata share of debt	$ 257	$ 247