CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 5,798	$ (28,052)	$ 37,902	$ (26,523)
Other comprehensive income:
Foreign currency translation adjustments	3,937	6,382	5,786	4,002
Pension adjustments, net	22	16	96	1,032
Net unrealized loss on available-for-sale securities	(14)		(14)
Total other comprehensive income	3,945	6,398	5,868	5,034
Comprehensive income (loss)	$ 9,743	$ (21,654)	$ 43,770	$ (21,489)