Retirement Benefit Plans - Roll Forward of Defined Benefit Pension Plan Obligations and Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Benefit obligations:
Benefit obligations at beginning of year	$ 20,888	$ 20,345
Service cost	174	181
Interest cost	944	1,072
Actuarial (gain) loss	(898)	1,313
Benefits paid	(1,874)	(2,023)
Benefit obligations at end of year	19,234	20,888
Plan assets:
Plan assets at beginning of year	18,376	17,194
Actual return on plan assets	1,568	3,076
Employer contributions	332	129
Benefits paid	(1,874)	(2,023)
Plan assets at end of year	18,402	18,376
Underfunded status at end of year	$ (832)	$ (2,512)