Retirement Benefit Plans - Components of Net Periodic Benefit Cost (Details) - United States - Pension Plan - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 75	$ 63
Interest cost	264	240
Expected return on plan assets	(393)	(402)
Amortization of net loss	107	161
Net periodic cost	$ 53	$ 62