Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance (in shares) at Sep. 30, 2019		55,535
Beginning Balance at Sep. 30, 2019	$ 744,949	$ 556	$ 407,628	$ 389,163	$ (52,398)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	1,695		1,695
Release of restricted stock (in shares)		463
Release of restricted stock	5	$ 5
Taxes paid related to net share settlement of equity awards	(1,395)		(1,395)
Foreign currency translation gain	6,071				6,071
Purchase and retirement of treasury stock (in shares)		(142)
Purchase and retirement of treasury stock	(963)	$ (2)	(488)	(473)
Net income	1,238			1,238
Ending Balance (in shares) at Dec. 31, 2019		55,856
Ending Balance at Dec. 31, 2019	751,600	$ 559	407,440	389,928	(46,327)
Beginning Balance (in shares) at Sep. 30, 2019		55,535
Beginning Balance at Sep. 30, 2019	744,949	$ 556	407,628	389,163	(52,398)
Ending Balance (in shares) at Sep. 30, 2020		55,303
Ending Balance at Sep. 30, 2020	649,127	$ 551	398,475	318,169	(68,068)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	524		524
Release of restricted stock (in shares)		296
Release of restricted stock	5	$ 5
Taxes paid related to net share settlement of equity awards	(730)		(730)
Foreign currency translation gain	11,277				11,277
Net income	4,299			4,299
Ending Balance (in shares) at Dec. 31, 2020		55,599
Ending Balance at Dec. 31, 2020	$ 664,502	$ 556	$ 398,269	$ 322,468	$ (56,791)