Summary of Significant Accounting Policies - Supplemental Disclosures of Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest income	$ (384)	$ 4	$ 70
Income taxes paid, net of refunds	(764)	(352)	2,298
Non-cash capital expenditures	$ 634	$ 221	$ 147