CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (56,254)	$ (310,826)	$ 45,893
Other comprehensive income (loss):
Foreign currency translation adjustments	5,620	(37,179)	(1,980)
Pension adjustments, net	(66)	2,233	(87)
Unrealized gain (loss) on available-for-sale securities	217	(425)	(10)
Total other comprehensive income (loss)	5,771	(35,371)	(2,077)
Comprehensive (loss) income	$ (50,483)	$ (346,197)	$ 43,816