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INVESTMENTS IN EQUITY INVESTEES - SCHEDULE OF COST METHOD INVESTMENTS (Details) (USD $) In Millions, unless otherwise specified | Mar. 31, 2014 Two Dot Wind Project in Montana [Member] MW | Mar. 31, 2014 Carroll Wind Project in Iowa [Member] MW | Sep. 30, 2012 OwnEnergy [Member]
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Schedule of Cost-method Investments [Line Items] |  |  |
Cost method investments | $ 22.0 | $ 42.0 | $ 8.8
Cost method investment, ownership percentage |  |  | 18.70%
Number of megawatts | 9.7 | 20 |

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