CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Non-controlling Interest [Member]	Total
Beginning balance at Dec. 31, 2017		$ 439	$ 399,426	$ (66,707)	$ 23,864	$ (175)	$ 12,144	$ 368,991
Beginning balance, shares at Dec. 31, 2017	1	43,931,484
Beginning balance, Treasury Stock, shares at Dec. 31, 2017						(18,348)
Adoption of ASC 606 at Dec. 31, 2017					247			247
Share-based compensation			2,374					2,374
Net (loss) income					10,978		887	11,865
Exercise of stock options		$ 3	350					353
Exercise of stock options, shares		275,653
Cemblend exchangeable shares		$ 4	(4)
Cemblend exchangeable shares, shares		442,312
Currency translation adjustment				(6,689)				(6,689)
Ending balance at Mar. 31, 2018		$ 446	402,146	(73,396)	35,089	$ (175)	13,031	377,141
Ending balance, shares at Mar. 31, 2018	1	44,649,449
Ending balance, Treasury Stock, shares at Mar. 31, 2018						(18,348)
Beginning balance at Dec. 31, 2018		$ 451	411,423	(84,030)	(166,206)	$ (337)	14,930	$ 176,231
Beginning balance, shares at Dec. 31, 2018	1	45,100,771
Beginning balance, Treasury Stock, shares at Dec. 31, 2018						(28,308)		(28,308)
Share-based compensation			2,968					$ 2,968
Net (loss) income					(11,966)		2,088	(9,878)
Shares withheld						$ (309)		(309)
Shares withheld, shares						(54,529)
Distribution to noncontrolling interest							(600)	(600)
Vesting of restricted stock		$ 2	(2)
Vesting of restricted stock, shares		168,563
Cemblend exchangeable shares		$ 13	(13)
Cemblend exchangeable shares, shares	(1)	1,326,935
Proceeds from the issuance of ESPP		$ 2	675					677
Proceeds from the issuance of ESPP, shares		156,486
Currency translation adjustment				1,537				1,537
Ending balance at Mar. 31, 2019		$ 468	$ 415,051	$ (82,493)	$ (178,172)	$ (646)	$ 16,418	$ 170,626
Ending balance, shares at Mar. 31, 2019		46,752,755
Ending balance, Treasury Stock, shares at Mar. 31, 2019						(82,837)		(82,837)