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ACQUISITION (Details) $ in Thousands |  |  | 12 Months Ended
--- | --- | --- | ---
Nov. 07, 2017 USD ($) | Oct. 27, 2017 USD ($) mi | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Sep. 30, 2016 USD ($)
Business Acquisition [Line Items] |  |  |  |  |
Initial payment |  |  | $ 10,000 | $ 0 | $ 0
Adelphia | Talen's Membership Interests In IEC |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Base purchase price |  | $ 166,000 |  |  |
Additional contingent consideration (up to $23 million) |  | $ 23,000 |  |  |
Initial payment | $ 10,000 |  |  |  |
Pipeline length owned | mi |  | 84 |  |  |
Transportation precedent agreement, period |  | 10 years |  |  |

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