Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 51,987	$ 6,239	$ (54,465)
Other comprehensive income (loss), net of tax:
Unrealized hedge gain (loss) arising during the period, net of tax of $0.2 million in 2018, $0.1 million in 2017 and $0 million in 2016, respectively	1,445	(758)	(3,375)
Net hedge (gain) loss reclassified into earnings, net of tax of ($0.1 million) in 2018, ($0.1 million) in 2017 and $0 million in 2016, respectively	483	459	2,131
Unrealized loss on hedging instruments	1,928	(299)	(1,244)
Foreign currency translation adjustment, net of tax of $0 for all periods	(11,767)	16,593	408
Unrealized loss on marketable securities, net of tax of $0 for all periods	(269)	(22)	(122)
Amortization of net actuarial pension loss included in net income, net of tax of ($0.7 million), ($1.0 million), and ($0.7 million) in 2018, 2017 and 2016, respectively	1,629	2,392	1,609
Pension net gain (loss) arising during the period net of tax of $1.5 million, ($3.6 million), and $3.5 million in 2018, 2017, and 2016, respectively	(3,787)	8,636	(8,646)
Change in unamortized pension loss during the period related to changes in foreign currency	588	(1,254)	(216)
Other comprehensive income (loss)	(11,678)	26,046	(8,211)
Comprehensive income (loss)	$ 40,309	$ 32,285	$ (62,676)