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INVESTMENTS IN EQUITY INVESTEES, COST METHOD INVESTMENTS (Details) (USD $) | 12 Months Ended |  |  |  |  |  | 3 Months Ended | 1 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2014 Wind Purchase Option [Member] | Oct. 09, 2014 Alexander Wind Project in Kansas [Member] Subsequent Event [Member] MWh | Sep. 30, 2014 Carroll Wind Project in Iowa [Member] MWh | Sep. 30, 2014 Two Dot Wind Project in Montana [Member] MWh | Sep. 30, 2012 OwnEnergy [Member] | Sep. 30, 2014 PennEast [Member] Investor mi | Oct. 31, 2014 PennEast [Member] Subsequent Event [Member] Investor
Schedule of Cost-method Investments [Line Items] |  |  |  |  |  |  |  |  |
Number of other investors which formed PennEast |  |  |  |  |  |  |  | 4 | 6
Construction plan, pipeline distance (in miles) |  |  |  |  |  |  |  | 108 |
Cost method investments |  |  |  |  |  |  | $ 8,800,000 |  |
Cost method investment, ownership percentage |  |  |  |  |  |  | 18.70% |  |
Number of megawatts of the wind project |  |  |  | 48 | 20 | 9.7 |  |  |
Solar and wind equipment, real estate properties and other, at cost | 347,285,000 | 249,516,000 | (2,400,000) |  |  |  |  |  |
Asset impairment loss | 6,400,000 |  |  |  |  |  |  |  |
Asset impairment loss, after tax | 3,800,000 |  |  |  |  |  |  |  |
Development project costs |  |  |  | $ 85,000,000 | $ 42,000,000 | $ 21,200,000 |  |  |

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