Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 1,123	$ 7,592	$ (4,457)
Other comprehensive income (loss):
Net changes related to available-for-sale securities, net of tax	(10)	64	(38)
Foreign currency translation adjustments	2,788	(2,386)	(661)
Other comprehensive income (loss)	2,778	(2,322)	(699)
Comprehensive income (loss)	$ 3,901	$ 5,270	$ (5,156)