Retirement Benefit Plans - Roll Forward of Defined Benefit Pension Plan Obligations and Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Benefit obligations:
Benefit obligations at beginning of year	$ 29,330	$ 31,793
Service cost	42	131
Interest cost	714	699
Actuarial (gain)	(5,265)	(967)
Benefits paid	(1,970)	(2,349)
Currency translation	(56)	23
Benefit obligations at end of year	22,795	29,330
Plan assets:
Plan assets at beginning of year	23,211	21,609
Actual return on plan assets	(3,376)	3,825
Employer contributions	72	126
Benefits paid	(1,970)	(2,349)
Plan assets at end of year	$ 17,937	$ 23,211