Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 3,926	$ 9,985	$ 11,947
Other comprehensive income (loss):
Unrealized holding gains (losses) on available-for-sale securities, net of tax	49	(68)	(1,208)
Reclassification adjustment for realized gain included in net income, net of tax			(315)
Foreign currency translation adjustments	2,095	1,336
Other comprehensive income (loss)	2,144	1,268	(1,523)
Comprehensive income	$ 6,070	$ 11,253	$ 10,424