Schedule of Valuation and Qualifying Accounts - Valuation and Qualifying Accounts (Detail) - Allowance for doubtful accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 200	$ 147	$ 230
Additions: Charges to Income	73	188	64
Deductions: Other Changes (Debit) Credit	(143)	(135)	(147)
Balance at End of Period	$ 130	$ 200	$ 147