Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	$ 38,690	$ 35,245	$ 36,054	$ 45,239	$ 46,421	$ 44,189
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	(5,604)		(5,667)
Retirement plan liability adjustment, net of tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	(7,205)		(7,642)
Total accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive loss	$ (12,809)	$ (12,928)	$ (13,309)	$ (9,001)	$ (8,949)	$ (8,629)