Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	$ 41,323	$ 38,689	$ 36,054	$ 38,062	$ 45,237	$ 44,189
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	(5,492)		(5,667)
Retirement plan liability adjustment, net of tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	(7,016)		(7,642)
Total accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	$ (12,508)	$ (12,809)	$ (13,309)	$ (8,748)	$ (9,002)	$ (8,629)