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EMPLOYEE BENEFIT PLANS (Details) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Apr. 30, 2018
Components of net periodic cost |  |  |  |  |
Discretionary contribution |  |  | $ 0 |  |
Postemployment benefits, expected future benefit payment |  |  |  |  | $ 6,400,000
Postemployment benefits, period expense |  |  | 4,600,000 |  |
Pension |  |  |  |  |
Components of net periodic cost |  |  |  |  |
Service cost | $ 2,035,000 | $ 2,086,000 | 6,104,000 | $ 6,260,000 |
Interest cost | 2,623,000 | 2,443,000 | 7,870,000 | 7,328,000 |
Expected return on plan assets | (4,910,000) | (4,829,000) | (14,729,000) | (14,485,000) |
Recognized actuarial loss | 1,884,000 | 2,207,000 | 5,653,000 | 6,620,000 |
Prior service cost amortization | 27,000 | 28,000 | 80,000 | 83,000 |
Net periodic benefit cost | 1,659,000 | 1,935,000 | 4,978,000 | 5,806,000 |
OPEB |  |  |  |  |
Components of net periodic cost |  |  |  |  |
Service cost | 1,152,000 | 1,095,000 | 3,455,000 | 3,285,000 |
Interest cost | 1,591,000 | 1,386,000 | 4,773,000 | 4,159,000 |
Expected return on plan assets | (1,338,000) | (1,192,000) | (4,014,000) | (3,575,000) |
Recognized actuarial loss | 1,165,000 | 1,093,000 | 3,495,000 | 3,278,000 |
Prior service cost amortization | (91,000) | (91,000) | (273,000) | (273,000) |
Net periodic benefit cost | $ 2,479,000 | $ 2,291,000 | $ 7,436,000 | $ 6,874,000 |

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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of contribution received by defined benefit plan from employer which increases plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(ii) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2709-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(01) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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