Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	$ 48,337	$ 47,708	$ 45,523	$ 41,323	$ 38,689	$ 36,054
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	(5,195)		(5,257)
Retirement plan liability adjustment, net of tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	(7,577)		(8,211)
Total accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	$ (12,772)	$ (13,062)	$ (13,468)	$ (12,508)	$ (12,809)	$ (13,309)