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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, 2019 USD ($) plan | Sep. 30, 2018 USD ($)
Retirement Benefits [Abstract] |  |
Multiemployer plans, number of plans | plan | 1 |
Contributions by the Company | $ | $ 55 | $ 60
Amortization period of losses utilized under pension fund | 30 years |

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