Schedule of Valuation and Qualifying Accounts - Valuation and Qualifying Accounts (Detail) - Allowance for doubtful accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 147	$ 230	$ 19
Additions Charged (Credited) to Expenses	188	64	222
Deductions From Reserves	135	147	11
Balance at End of Period	$ 200	$ 147	$ 230