Leases - Balance Sheet Classification and Amounts of Right-of-Use Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Right-of-use assets:
Other assets	$ 2,478	$ 2,508
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating lease liabilities:
Other accrued liabilities	$ 456	$ 436
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherAccruedLiabilitiesCurrent	us-gaap:OtherAccruedLiabilitiesCurrent
Other long-term liabilities	$ 3,411	$ 3,340
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Total operating lease liabilities	$ 3,867	$ 3,776