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EMPLOYEE BENEFIT PLANS - ASSUMED HCCTR (Details) - OPEB - USD ($) $ in Thousands | 12 Months Ended
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Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
HCCTR | 6.60% | 6.90% | 7.60%
Ultimate HCCTR | 4.50% | 4.50% | 4.50%
Effect of a 1 percentage point increase in the HCCTR on: |  |  |
Year-end benefit obligation | $ 26,710 | $ 43,217 | $ 49,106
Total service and interest cost | 2,544 | 2,959 | 2,799
Effect of a 1 percentage point decrease in the HCCTR on: |  |  |
Year-end benefit obligation | (21,853) | (34,669) | (38,844)
Total service and interest costs | $ (1,966) | $ (2,253) | $ (2,151)

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- Definition Defined Benefit Plan, Effect of One-Percentage Point Increase in Assumed Health Care Cost Trend Rates [Abstract] + References No definition available. + Details
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- Definition Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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