v2.4.0.6

Variable Interest Entities and Unconsolidated Investments (Consolidation of VIE) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2011 | Dec. 31, 2010
--- | --- | ---
Schedule of Equity Method Investments [Line Items] |  |
Power generation capacity | 11,391 | 13,656
Power generation capacity under construction | 584 | 1,029
Equity Method Investment, Ownership Percentage | 50.00% |
Los Esteros Project [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Power generation capacity | 188 |
Power generation capacity after upgrade | 308 |
Russell City Energy [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Equity Method Investment, Ownership Percentage | 75.00% |
Minority Interest Ownership Percentage By Noncontrolling Third Party Owners | 25.00% |
Los Esteros Project [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Debt Instrument, Face Amount | 373 |

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