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RETIREMENT PLANS - NARRATIVE (Details) - USD ($) $ in Thousands | 12 Months Ended
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Sep. 30, 2021 | Sep. 30, 2020
Retirement plans |  |
Curtailment gain and gain on termination of post-retirement medical plan in OCI | $ 541 | $ 1,726
Gain on termination of post-retirement medical plan | $ 2,341 | 0
Pension Plan |  |
Retirement plans |  |
Period of employee's highest average earnings on which benefits are based | 5 years |
Expected future contributions | $ 0 |
Accumulated benefit obligation | $ 10,365 | 10,280
Post-retirement Medical |  |
Retirement plans |  |
Minimum period of service to be attained for being covered under the plan | 20 years |
Minimum period of service to be attained at the position of Vice President or higher for being covered under the plan | 10 years |
Curtailment gain and gain on termination of post-retirement medical plan in OCI | $ 541 | 0
Gain on termination of post-retirement medical plan | 2,341 |
Pension Plan And Supplemental Employee Retirement Plan |  |
Retirement plans |  |
Curtailment gain and gain on termination of post-retirement medical plan in OCI | 0 | 1,726
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax |  | 1,726
SERP |  |
Retirement plans |  |
Accumulated benefit obligation | $ 2,136 | $ 2,031

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- Definition Represents the highest consecutive number of years of service in which the average earnings are used to calculate the basis of plan benefits. + References No definition available. + Details
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- Definition The minimum period for which the individual is required to perform services in order to be covered under the defined benefit and other postretirement plans. + References No definition available. + Details
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- Definition The minimum period for which the individual is required to perform services at the position of Vice President or higher in order to be covered under the defined benefit and other postretirement plans. + References No definition available. + Details
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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921 + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from settlement and curtailment. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 + Details
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