Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 1,534	$ 506	$ (22)	$ 2,806
Other comprehensive income (loss):
Unrealized holding (losses) gains on available-for-sale securities, net of tax	(28)	4	(41)	50
Foreign currency translation adjustments	1,207	660	1,837	(1,594)
Other comprehensive income (loss)	1,179	664	1,796	(1,544)
Comprehensive income	$ 2,713	$ 1,170	$ 1,774	$ 1,262