Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (27,460)	$ 51,987	$ 6,239
Other comprehensive income (loss), net of tax:
Hedge gain (loss) arising during the period, net of tax of $1.7 million, $0.2 million and $0.1 million in 2019, 2018 and 2017, respectively.	5,251	1,445	(758)
Net hedge gain (loss) reclassified into earnings, net of tax of $0.1 million in 2019, 2018 and 2017, respectively.	(549)	483	459
Realized and unrealized gain (loss) on hedging instruments	4,702	1,928	(299)
Foreign currency translation adjustment, net of tax of $0 for all periods	(24,755)	(11,767)	16,593
Unrealized gain (loss) on marketable securities, net of tax of $0 for all periods	530	(269)	(22)
Amortization of net actuarial pension loss included in net income, net of tax of $0.7 million in in 2019, 2018, respectively, and $1.0 million and 2017	1,691	1,629	2,392
Pension net gain (loss) arising during the period net of tax of $3.6 million, $1.5 million, and $3.6 million in 2019, 2018, and 2017, respectively	(8,743)	(3,787)	8,636
Change in unamortized pension loss during the period related to changes in foreign currency	1,450	588	(1,254)
Other comprehensive income (loss)	(25,125)	(11,678)	26,046
Comprehensive income (loss)	$ (52,585)	$ 40,309	$ 32,285