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) Income	Noncontrolling Interest
Beginning Balance at Sep. 30, 2016	$ 594,205	$ 541	$ 318,723	$ 319,808	$ (44,089)	$ (778)
Beginning balance (shares) at Sep. 30, 2016		54,099
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	3,575		3,575
Release of restricted stock	2	$ 2
Release of restricted stock (shares)		193
Taxes paid related to net share settlement of equity awards	(767)		(767)
Foreign currency translation adjustment	1,555				1,545	10
Net income (loss)	14,894			15,188		(294)
Ending Balance at Mar. 31, 2017	613,464	$ 543	321,531	334,996	(42,544)	(1,062)
Ending balance (shares) at Mar. 31, 2017		54,292
Beginning Balance at Sep. 30, 2017	659,926	$ 544	348,532	351,666	(38,367)	(2,449)
Beginning balance (shares) at Sep. 30, 2017		54,398
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	5,477		5,477
Release of restricted stock	1	$ 1
Release of restricted stock (shares)		66
Taxes paid related to net share settlement of equity awards	(311)		(311)
Reclassification of stranded tax effects resulting from the Tax Cuts and Jobs Act	0			1,455	(1,455)
Foreign currency translation adjustment	(535)				(641)	106
Net income (loss)	23,572			24,561		(989)
Ending Balance at Mar. 31, 2018	$ 688,130	$ 545	$ 353,698	$ 377,682	$ (40,463)	$ (3,332)
Ending balance (shares) at Mar. 31, 2018		54,464