Summary of Significant Accounting Policies and Select Balance Sheet Information - Balance Sheet Classification and Amounts of Right-of-Use Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Right-of-use assets:
Other assets	$ 2,435	$ 2,508
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	us-gaap:OtherAssets
Operating lease liabilities:
Other accrued liabilities	$ 518	436
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	us-gaap:OtherLiabilitiesCurrent
Operating lease liabilities	$ 3,188	3,340
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other long-term liabilities
Total operating lease liabilities	$ 3,706	$ 3,776