Summary of Significant Accounting Policies and Select Balance Sheet Information - Summary of Other Noncurrent Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Schedule of Investments [Line Items]
Other assets, net	$ 3,718	$ 4,269
Operating Lease Right-of-Use Assets [Member]
Schedule of Investments [Line Items]
Other assets, net	2,435	2,508
Other Noncurrent Assets [Member]
Schedule of Investments [Line Items]
Other assets, net	$ 1,283	$ 1,761