Retirement Benefit Plans - Net Plan Assets Recognized in the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of funded status:
Plan assets less than projected benefit obligations	$ (5,385)	$ (6,230)
Amounts recognized in accumulated other comprehensive loss:
Net loss, plans in which benefit obligations exceed assets	7,432	8,406
Net amount recognized in the consolidated balance sheets, Plans in which Benefit Obligations Exceed Assets	2,047	2,176
Amounts recognized in the consolidated balance sheets are:
Accumulated other comprehensive loss pretax, Plans in which Benefit Obligations Exceed Assets	7,432	8,406
Accrued liabilities
Amounts recognized in the consolidated balance sheets are:
Liabilities	46	46
Pension liability
Amounts recognized in the consolidated balance sheets are:
Liabilities	$ 5,339	$ 6,184