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, 2025	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 18,402	$ 18,376	$ 17,194
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	18,402	18,376
Large blend
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	3,499	3,796
Large blend | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	3,499	3,796
Large growth
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,712	1,458
Large growth | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,712	1,458
Mid blend
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	861	775
Mid blend | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	861	775
Small growth
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	679	633
Small growth | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	679	633
Foreign large blend
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	614	770
Foreign large blend | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	614	770
Diversified emerging markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,034	338
Diversified emerging markets | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,034	338
Global equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	826	702
Global equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	826	702
Intermediate term bond
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	4,977	5,764
Intermediate term bond | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	4,977	5,764
Multi-sector bond
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	3,956	3,697
Multi-sector bond | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	3,956	3,697
Cash or money market
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	244	443
Cash or money market | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 244	$ 443