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Revenue and Vendor Concentrations - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Revenue, Major Customer [Line Items]
Revenue	$ 14,277	$ 11,419	$ 26,413	$ 20,688
Accounts receivable, net	7,797		7,797		$ 7,099
Customer Concentration Risk \| Sales Revenue Net
Revenue, Major Customer [Line Items]
Revenue	5,800	2,900	$ 5,900	$ 4,800
Total revenue, percentage			22.00%	23.00%
Customer Concentration Risk \| Accounts Receivable
Revenue, Major Customer [Line Items]
Accounts receivable, net	$ 2,400	$ 1,400	$ 2,400	$ 1,400
Customer Concentration Risk \| Customer One \| Sales Revenue Net
Revenue, Major Customer [Line Items]
Total revenue, percentage	24.00%	14.00%
Customer Concentration Risk \| Customer Two \| Sales Revenue Net
Revenue, Major Customer [Line Items]
Total revenue, percentage	17.00%	12.00%
Geographic Concentration Risk \| Sales Revenue Net
Revenue, Major Customer [Line Items]
Total revenue, percentage	23.00%	14.00%	26.00%	14.00%