CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 142,828	$ 39,215	$ 110,043
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	19,286	(8,548)	679
Minimum pension liability adjustment	1,047	(449)	(26)
Net unrealized loss on cash flow hedges	(10,711)	(18,780)	(63)
Other comprehensive income (loss), net of tax	9,622	(27,777)	590
Comprehensive income	$ 152,450	$ 11,438	$ 110,633