Retirement Benefit Plans - Amounts in Accumulated Other Comprehensive Loss Expected to be Recognized as Components of Net Periodic Benefit Costs (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2018 USD ($)
Defined Benefit Plan, Expected Amortization, Next Fiscal Year [Abstract]
Net loss, plans in which assets exceed benefit obligations	$ 0
Net loss, plans in which benefit obligations exceed assets	$ 426