Other Assets - Summary of Other Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Schedule of Investments [Line Items]
Other assets	$ 4,696	$ 4,269
Operating Lease Right-of-Use Assets [Member]
Schedule of Investments [Line Items]
Other assets	2,519	2,508
Other Noncurrent Assets [Member]
Schedule of Investments [Line Items]
Other assets	$ 2,177	$ 1,761