CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 707	$ (4,729)	$ (5,146)	$ (14,209)
Other comprehensive income (loss):
Change in unrealized gains (losses) on available-for-sale securities, net of tax	19	(38)	83	(89)
Foreign currency translation adjustments	238	1,039	20	834
Total other comprehensive income	257	1,001	103	745
Total comprehensive income (loss)	$ 964	$ (3,728)	$ (5,043)	$ (13,464)