Schedule of Valuation and Qualifying Accounts - Valuation and Qualifying Accounts (Detail) - Allowance for doubtful accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 230	$ 19	$ 10
Additions Charged (Credited) to Expenses	64	222	9
Deductions From Reserves	147	11
Balance at End of Period	$ 147	$ 230	$ 19