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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The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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