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, 2017		54,398
Beginning Balance at Sep. 30, 2017	$ 656,355	$ 544	$ 348,532	$ 347,885	$ (38,157)	$ (2,449)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	2,889		2,889
Release of restricted stock (shares)		66
Release of restricted stock	1	$ 1
Taxes paid related to net share settlement of equity awards	(311)		(311)
Foreign currency translation loss	(6,474)				(6,434)	(40)
Net income (loss)	12,024			12,639		(615)
Ending balance (shares) at Dec. 31, 2017		54,464
Ending Balance at Dec. 31, 2017	664,484	$ 545	351,110	360,524	(44,591)	(3,104)
Beginning balance (shares) at Sep. 30, 2017		54,398
Beginning Balance at Sep. 30, 2017	656,355	$ 544	348,532	347,885	(38,157)	(2,449)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	23,231
Ending balance (shares) at Mar. 31, 2018		54,464
Ending Balance at Mar. 31, 2018	684,224	$ 545	353,698	373,560	(40,247)	(3,332)
Beginning balance (shares) at Dec. 31, 2017		54,464
Beginning Balance at Dec. 31, 2017	664,484	$ 545	351,110	360,524	(44,591)	(3,104)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	2,588		2,588
Reclassification of stranded tax effects resulting from the Tax Cuts and Jobs Act	0			1,455	(1,455)
Foreign currency translation loss	5,945				5,799	146
Net income (loss)	11,207			11,581		(374)
Ending balance (shares) at Mar. 31, 2018		54,464
Ending Balance at Mar. 31, 2018	684,224	$ 545	353,698	373,560	(40,247)	(3,332)
Beginning balance (shares) at Sep. 30, 2018		54,585
Beginning Balance at Sep. 30, 2018	739,408	$ 546	397,927	386,622	(42,356)	(3,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	2,247		2,247
Release of restricted stock (shares)		860
Release of restricted stock	8	$ 8
Taxes paid related to net share settlement of equity awards	(3,288)		(3,288)
Transfer of subsidiary shares to noncontrolling interest	0		3,195			(3,195)
Foreign currency translation loss	(6,383)				(6,383)
Net income (loss)	(3,843)			(3,366)		(477)
Ending balance (shares) at Dec. 31, 2018		55,445
Ending Balance at Dec. 31, 2018	728,149	$ 554	400,081	383,256	(48,739)	(7,003)
Beginning balance (shares) at Sep. 30, 2018		54,585
Beginning Balance at Sep. 30, 2018	739,408	$ 546	397,927	386,622	(42,356)	(3,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(1,202)
Ending balance (shares) at Mar. 31, 2019		55,445
Ending Balance at Mar. 31, 2019	739,759	$ 554	402,505	386,650	(49,950)	0
Beginning balance (shares) at Dec. 31, 2018		55,445
Beginning Balance at Dec. 31, 2018	728,149	$ 554	400,081	383,256	(48,739)	(7,003)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation	2,424		2,424
Deconsolidation of subsidiary	7,756					7,756
Foreign currency translation loss	(1,211)				(1,211)
Net income (loss)	2,641			3,394		(753)
Ending balance (shares) at Mar. 31, 2019		55,445
Ending Balance at Mar. 31, 2019	$ 739,759	$ 554	$ 402,505	$ 386,650	$ (49,950)	$ 0