CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (11,804)	$ 707	$ (13,093)	$ (5,146)
Other comprehensive income (loss):
Change in unrealized gains on available-for-sale securities, net of tax		19		83
Foreign currency translation adjustments	(1,017)	238	(451)	20
Total other comprehensive income (loss)	(1,017)	257	(451)	103
Total comprehensive income (loss)	$ (12,821)	$ 964	$ (13,544)	$ (5,043)