CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Treasury Stock	Total
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
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				(7,369)		(7,369)
Changes in unrealized losses on marketable securities, net of tax effects			10			10
Actuarial losses, net of tax effects			(12)			(12)
Net income				13,057		13,057
Foreign currency translation adjustments			9,645			9,645
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
Beginning Balance at Sep. 30, 2020	$ 873	1,942,850	21,919	(551,072)	(200,956)	$ 1,213,614
Beginning Balance (in shares) at Sep. 30, 2020	87,293,710					73,831,841
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under restricted stock and purchase plans, net	$ 4	(4)
Shares issued under restricted stock and purchase plans, net (in shares)	378,422
Stock-based compensation		6,710				$ 6,710
Common stock dividends declared				(7,424)		(7,424)
Actuarial losses, net of tax effects			(38)			(38)
Net income				26,028		26,028
Foreign currency translation adjustments			13,264			13,264
Ending Balance at Dec. 31, 2020	$ 877	$ 1,949,556	$ 35,145	$ (532,468)	$ (200,956)	$ 1,252,154
Ending Balance (in shares) at Dec. 31, 2020	87,672,132					74,210,263