Leases - Balance Sheet Classification and Amounts of Right-of-Use Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Right-of-use assets:
Other assets	$ 2,406	$ 2,508
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets	Other assets
Operating lease liabilities:
Other accrued liabilities	$ 464	$ 436
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued other	Accrued other
Other long-term liabilities	$ 3,293	$ 3,340
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities
Total operating lease liabilities	$ 3,757	$ 3,776