Summary of Operations and Significant Accounting Policies - Inventories - Additional Information (Details)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Minimum
Inventory [Line Items]
Percentage of FIFO basis inventory	90.00%	90.00%
Purchase order commitment period	30 days
Maximum
Inventory [Line Items]
Purchase order commitment period, description	180 days or longer