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Retirement Benefit Plans - Asset Allocation of Defined Benefit Pension Plan Assets and Fair Values and Levels in Fair Value Hierarchy (Details) - USD ($) $ in Thousands | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | $ 18,376 | $ 17,194 | $ 17,937
Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 18,376 | 17,194 |
Large value |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | 879 |
Large value | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | 879 |
Large blend |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 3,796 | 3,124 |
Large blend | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 3,796 | 3,124 |
Large growth |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 1,458 | 1,060 |
Large growth | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 1,458 | 1,060 |
Mid blend |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 775 | 599 |
Mid blend | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 775 | 599 |
Small blend |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 633 | 499 |
Small blend | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 633 | 499 |
Foreign large blend |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 770 | 615 |
Foreign large blend | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 770 | 615 |
Diversified emerging markets |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 338 | 272 |
Diversified emerging markets | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 338 | 272 |
Global equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 702 | 577 |
Global equity securities | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 702 | 577 |
Intermediate term bond |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 5,764 | 5,676 |
Intermediate term bond | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 5,764 | 5,676 |
Multi-sector bond |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 3,697 |  |
Multi-sector bond | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 3,697 |  |
High inflation bond |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | 2,044 |
High inflation bond | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | 2,044 |
Cash or money market |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | 443 |  |
Cash or money market | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value | $ 443 |  |
Short-term bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | 1,849 |
Short-term bonds | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets at fair value |  | $ 1,849 |

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