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 (shares) at Sep. 30, 2016		54,099
Beginning Balance at Sep. 30, 2016	$ 594,205	$ 541	$ 318,723	$ 319,808	$ (44,089)	$ (778)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	5,126		5,126
Release of restricted stock (shares)		198
Release of restricted stock	2	$ 2
Taxes paid related to net share settlement of equity awards	(767)		(767)
Reclassification of Cash Convertible Notes Warrants to liabilities	(523)		(523)
Foreign currency translation adjustment	6,163				6,168	(5)
Net income (loss)	20,096			20,448		(352)
Ending balance (shares) at Jun. 30, 2017		54,297
Ending Balance at Jun. 30, 2017	624,302	$ 543	322,559	340,256	(37,921)	(1,135)
Beginning balance (shares) at Sep. 30, 2017		54,398
Beginning Balance at Sep. 30, 2017	659,926	$ 544	348,532	351,666	(38,367)	(2,449)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	8,150		8,150
Release of restricted stock (shares)		66
Release of restricted stock	1	$ 1
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	(8,111)				(8,218)	107
Equity classified conversion feature of 2025 Convertible Notes, net of tax	39,057		39,057
Net income (loss)	37,846			39,194		(1,348)
Ending balance (shares) at Jun. 30, 2018		54,464
Ending Balance at Jun. 30, 2018	$ 736,558	$ 545	$ 395,428	$ 392,315	$ (48,040)	$ (3,690)