Retirement Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Retirement Benefits [Abstract]
Service cost	$ 74	$ 63	$ 224	$ 189
Interest cost	264	240	791	719
Expected return on plan assets	(393)	(402)	(1,180)	(1,205)
Amortization of net loss	107	161	322	483
Net periodic cost	$ 52	$ 62	$ 157	$ 186