Schedule of Valuation and Qualifying Accounts - Valuation and Qualifying Accounts (Detail) - Allowance for doubtful accounts [Member] - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		$ 81	$ 119	$ 130
Additions: Charges to Income		37	5	(11)
Deductions: Other Changes (Debit) Credit	[1]	(38)	(43)
Balance at End of Period		$ 80	$ 81	$ 119

[1] Primarily consists of uncollectible accounts written off, less recoveries.