Retirement Benefit Plans - Net Pension Expense for Defined Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Retirement Benefits [Abstract]
Service cost	$ 24	$ 42
Interest cost	1,090	714
Expected return on plan assets	(1,101)	(1,362)
Amortization of net loss	319	476
Settlement cost	108	208
Net pension expense for defined benefit plans (non-operating expense)	$ 440	$ 78
Interest cost	Interest cost
Expected return on plan assets	Expected return on plan assets
Amortization of net loss	Amortization of net loss
Settlement cost	Settlement cost