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Equity method investments (Details) (Brazilian Transmission Lines [Member], USD $) In Millions, unless otherwise specified | 6 Months Ended |  |
--- | --- | --- | ---
Jun. 30, 2011 | Dec. 31, 2010 | Jun. 30, 2010
Brazilian Transmission Lines [Member] |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Number of separate parties with which company entered into agreements to sell equity ownership interests | 3 |  |
Ownership interest in ECTE sold (in hundredths) | 59.96% |  |
Number of years over which remaining ownership interest in ECTE will be sold (in years) | 4 |  |
Total assets of equity method investments | $ 107.7 | $ 107.4 | $ 369.9
Total long-term debt of equity method investments | 49.6 | 30.1 | 157.1
Investment in equity method investments | 11.4 | 10.9 | 57.9
Undistributed earnings of equity method investments | $ 2.1 | $ 1.9 | $ 11.1

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