Retirement Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Retirement Benefits [Abstract]
Service cost	$ 11	$ 26
Interest cost	178	175
Expected return on plan assets	(340)	(355)
Amortization of net loss	119	211
Net periodic cost	$ (32)	$ 57