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, 2018	$ 841	$ 1,898,434	$ 13,587	$ (994,074)	$ (200,956)	$ 717,832
Beginning Balance (in shares) at Sep. 30, 2018	84,164,130
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under restricted stock and purchase plans, net	$ 13	(13)
Shares issued under restricted stock and purchase plans, net (in shares)	1,252,908
Stock-based compensation		4,467				4,467
Common stock dividends declared, at $0.10 per share				(7,208)		(7,208)
Foreign currency translation adjustments			1,677			1,677
Changes in unrealized losses on marketable securities, net of tax effects of $0 and ($38) during the three months ended December 31, 2019 and 2018, respectively			(121)			(121)
Actuarial losses, net of tax effects of $1 and $2 during the three months ended December 31, 2019 and 2018			(9)			(9)
Cumulative effect of adoption of ASC 606				(858)		(858)
Net income				14,415		14,415
Ending Balance at Dec. 31, 2018	$ 854	1,902,888	15,134	(987,725)	(200,956)	730,195
Ending Balance (in shares) at Dec. 31, 2018	85,417,038
Beginning Balance at Sep. 30, 2019	$ 857	1,921,954	3,511	(586,412)	(200,956)	$ 1,138,954
Beginning Balance (in shares) at Sep. 30, 2019	85,759,700					72,297,831
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under restricted stock and purchase plans, net	$ 14	(14)
Shares issued under restricted stock and purchase plans, net (in shares)	1,320,317
Stock-based compensation		4,410				$ 4,410
Common stock dividends declared, at $0.10 per share				(7,369)		(7,369)
Foreign currency translation adjustments			9,645			9,645
Changes in unrealized losses on marketable securities, net of tax effects of $0 and ($38) during the three months ended December 31, 2019 and 2018, respectively			10			10
Actuarial losses, net of tax effects of $1 and $2 during the three months ended December 31, 2019 and 2018			(12)			(12)
Net income				13,057		13,057
Ending Balance at Dec. 31, 2019	$ 871	$ 1,926,350	$ 13,154	$ (580,724)	$ (200,956)	$ 1,158,695
Ending Balance (in shares) at Dec. 31, 2019	87,080,017					73,618,148