Retirement Benefit Plans - Net Plan Assets Recognized in the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Reconciliation of funded status:
Plan assets less than projected benefit obligations	$ (10,211)	$ (9,574)
Amounts recognized in accumulated other comprehensive loss:
Net loss	11,973	11,404
Net amount recognized in the consolidated balance sheets	1,762	1,830
Amounts recognized in the consolidated balance sheets are:
Accumulated other comprehensive loss – pretax	11,973	11,404
Accrued liabilities
Amounts recognized in the consolidated balance sheets are:
Liabilities	(46)	(46)
Pension liability
Amounts recognized in the consolidated balance sheets are:
Liabilities	$ (10,165)	$ (9,528)