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Inventories - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Sep. 30, 2018
Inventory Disclosure [Abstract]          
Percentage of inventories determined using LIFO method 37.00%   37.00%   54.00%
Additional amount that would have been reported in inventory if FIFO method had been used $ 8,469   $ 8,469   $ 8,879
Inventory [Line Items]          
Cost of goods sold $ (23,486) $ (25,402) (75,119) $ (72,889)  
Accounting Standards Update 2014-09          
Inventory [Line Items]          
Cost of goods sold     $ 210