Retirement Benefit Plans - Changes in the Fair Value of Level 3 Defined Benefit Plan Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Changes in the fair value of the Company's Level 3 investments
Plan assets at beginning of year	$ 23,211	$ 21,609
Actual return on plan assets	(3,376)	3,825
Plan assets at end of year	17,937	23,211
Level 3
Changes in the fair value of the Company's Level 3 investments
Plan assets at beginning of year	2,108	2,098
Actual return on plan assets	(279)	52
Purchases and sales of plan assets, net	0	(42)
Plan assets at end of year	$ 1,829	$ 2,108