Retirement Benefit Plans - Net Plan Assets Recognized in the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Reconciliation of funded status:
Plan assets less than projected benefit obligations	$ (6,119)	$ (10,211)
Amounts recognized in accumulated other comprehensive loss:
Net loss	7,482	11,973
Net amount recognized in the consolidated balance sheets	1,363	1,762
Amounts recognized in the consolidated balance sheets are:
Accumulated other comprehensive loss – pretax	7,482	11,973
Accrued liabilities
Amounts recognized in the consolidated balance sheets are:
Liabilities	(46)	(46)
Pension liability
Amounts recognized in the consolidated balance sheets are:
Liabilities	$ (6,073)	$ (10,165)