Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 6,239	$ (54,465)	$ 47,557
Other comprehensive income (loss), net of tax:
Unrealized hedge gain (loss) arising during the period, net of tax of $0.1 million in 2017 and $0 million in 2016 and 2015, respectively	(758)	(3,375)	0
Net hedge (gain) loss reclassified into earnings, net of tax of $0.1 million in 2017 and $0 million in 2016 and 2015, respectively	459	2,131	0
Unrealized loss on hedging instruments	(299)	(1,244)	0
Foreign currency translation adjustment, net of tax of $0 for all periods	16,593	408	(47,177)
Unrealized loss on marketable securities, net of tax of $0 for all periods	(22)	(122)	0
Amortization of net actuarial pension loss included in net income, net of tax of $1.0 million, $0.7 million, and $18.5 million in 2017, 2016 and 2015, respectively	2,392	1,609	52,249
Pension net gain (loss) arising during the period net of tax of ($3.6 million), $3.5 million and $1.6 million in 2017, 2016, and 2015, respectively	8,636	(8,646)	(4,797)
Change in unamortized pension loss during the period related to changes in foreign currency	(1,254)	(216)	2,350
Other comprehensive income (loss)	26,046	(8,211)	2,625
Comprehensive income (loss)	$ 32,285	$ (62,676)	$ 50,182