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Retirement Benefit Plans - Schedule of Contributions in U.S. Multi-Employer Retirement Plan for Certain Union Employees (Details) $ in Thousands | 12 Months Ended
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Sep. 30, 2020 USD ($) plan | Sep. 30, 2019 USD ($)
Retirement Benefits [Abstract] |  |
Multiemployer plans, number of plans | plan | 1 |
Contributions by the Company | $ | $ 0 | $ 55
Amortization period of losses utilized under pension fund | 30 years |

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- Definition Amount of cost for employer contribution to multiemployer pension plan determined to be individually significant. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 5 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=35742348&loc=SL14450788-114948 + Details
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