CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Treasury Stock	Total
Beginning Balance at Sep. 30, 2014	$ 804	$ 1,834,619	$ 15,687	$ (1,007,265)	$ (200,956)	$ 642,889
Beginning Balance (in shares) at Sep. 30, 2014	80,375,777
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock option, restricted stock and purchase plans, net	$ 7	(421)				(414)
Shares issued under stock option, restricted stock and purchase plans, net (in shares)	717,275
Stock-based compensation		12,159				12,159
Common stock dividend declared, at $0.40, $0.40 and $0.40 per share for fiscal years 2017, 2016 and 2015, respectively				(27,021)		(27,021)
Comprehensive income (loss):
Net income (loss)				14,221		14,221
Foreign currency translation adjustments			(9,557)			(9,557)
Changes in unrealized gains (losses) on marketable securities, net of tax effects of $0, $58, and $(83) for fiscal years 2017, 2016 and 2015, respectively			141			141
Actuarial gains (losses) arising in the year, net of tax effects of $(74), $161, and $115 for fiscal years 2017, 2016 and 2015, respectively			(605)			(605)
Recognition of pension settlement in earnings			232			232
Ending Balance at Sep. 30, 2015	$ 811	1,846,357	5,898	(1,020,065)	(200,956)	632,045
Ending Balance (in shares) at Sep. 30, 2015	81,093,052
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock option, restricted stock and purchase plans, net	$ 10	(2,391)				(2,381)
Shares issued under stock option, restricted stock and purchase plans, net (in shares)	1,127,218
Stock-based compensation		11,737				11,737
Common stock dividend declared, at $0.40, $0.40 and $0.40 per share for fiscal years 2017, 2016 and 2015, respectively				(27,503)		(27,503)
Comprehensive income (loss):
Net income (loss)				(69,476)		(69,476)
Foreign currency translation adjustments			8,844			8,844
Changes in unrealized gains (losses) on marketable securities, net of tax effects of $0, $58, and $(83) for fiscal years 2017, 2016 and 2015, respectively			(106)			(106)
Actuarial gains (losses) arising in the year, net of tax effects of $(74), $161, and $115 for fiscal years 2017, 2016 and 2015, respectively			(322)			(322)
Pension curtailment (settlement)			852			852
Ending Balance at Sep. 30, 2016	$ 821	1,855,703	15,166	(1,117,044)	(200,956)	$ 553,690
Ending Balance (in shares) at Sep. 30, 2016	82,220,270					68,758,401
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock option, restricted stock and purchase plans, net	$ 12	1,937				$ 1,949
Shares issued under stock option, restricted stock and purchase plans, net (in shares)	1,074,578
Stock-based compensation		17,278				17,278
Common stock dividend declared, at $0.40, $0.40 and $0.40 per share for fiscal years 2017, 2016 and 2015, respectively				(27,932)		(27,932)
Comprehensive income (loss):
Net income (loss)				62,612		62,612
Foreign currency translation adjustments			(221)			(221)
Changes in unrealized gains (losses) on marketable securities, net of tax effects of $0, $58, and $(83) for fiscal years 2017, 2016 and 2015, respectively			2			2
Actuarial gains (losses) arising in the year, net of tax effects of $(74), $161, and $115 for fiscal years 2017, 2016 and 2015, respectively			525			525
Pension curtailment (settlement)			(259)			(259)
Ending Balance at Sep. 30, 2017	$ 833	$ 1,874,918	$ 15,213	$ (1,082,364)	$ (200,956)	$ 607,644
Ending Balance (in shares) at Sep. 30, 2017	83,294,848					69,832,979