Retirement Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Retirement Benefits [Abstract]
Service cost	$ 11	$ 26	$ 21	$ 52
Interest cost	178	175	357	350
Expected return on plan assets	(340)	(355)	(681)	(711)
Amortization of net loss	119	211	238	423
Net periodic cost	$ (32)	$ 57	$ (65)	$ 114