Inventories - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Inventory [Line Items]
Additional amount that would have been reported in inventory if FIFO method had been used	$ 8,296	$ 8,879
LIFO (benefit) expense	(75)	560
Cost of goods sold	(101,817)	$ (101,110)
Accounting Standards Update 2014-09
Inventory [Line Items]
Cost of goods sold	$ 340