Summary of Significant Accounting Policies - Reclassification Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	$ 159	$ (43)
Net loss	8,692	9,640
Amount reclassified from accumulated other comprehensive loss | Net actuarial gain
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes	1,659	1,003
Amount reclassified from accumulated other comprehensive loss | Settlements/curtailments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes	108	208
Amount reclassified from accumulated other comprehensive loss | Retirement Plan Liability Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes	1,767	1,211
Income tax expense	0	0
Net loss	$ 1,767	$ 1,211