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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, PENSION AND POSTEMPLOYMENT PLANS (Details) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2015 USD ($) | Sep. 30, 2016 USD ($) plan | Sep. 30, 2015 USD ($) | Sep. 30, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Number of noncontributory defined benefit retirement plans (in plans) | plan |  | 2 |  |
Employer contributions | $ | $ 30,000 |  | $ 0 |
Number of noncontributory medical and life insurance plans (in plans) | plan |  | 2 |  |
OPEB |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Employer contributions | $ |  | $ 3,235 | $ 5,672 | $ 5,000

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