Unaudited Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Total Stockholders' Equity	Noncontrolling interest
Beginning balance (in shares) at Dec. 31, 2017		73,822,001
Beginning balance at Dec. 31, 2017	$ 266,056	$ 386	$ 492,509	$ (222,833)	$ (7,965)	$ (52)	$ 262,045	$ 4,011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	3,122		3,122				3,122
Issuance of common stock through vesting of restricted stock units and option exercises (in shares)		271,517
Issuance of common stock through vesting of restricted stock units and option exercises	41	$ 2	39				41
Employee stock purchase plan (in shares)		196,360
Employee stock purchase plan	919	$ 1	918				919
Repurchases of common stock (in shares)		(25,387)
Repurchases of common stock	(118)				(118)		(118)
Foreign currency translation adjustment	(113)					(63)	(63)	(50)
Net Income (loss)	(2,436)			(1,918)			(1,918)	(518)
Other	(4)			(1)		(3)	(4)
Ending balance (in shares) at Mar. 31, 2018		74,264,491
Ending balance at Mar. 31, 2018	267,467	$ 389	496,588	(224,752)	(8,083)	(118)	264,024	3,443
Beginning balance (in shares) at Dec. 31, 2017		73,822,001
Beginning balance at Dec. 31, 2017	$ 266,056	$ 386	492,509	(222,833)	(7,965)	(52)	262,045	4,011
Ending balance (in shares) at Dec. 31, 2018	75,375,341	75,375,341
Ending balance at Dec. 31, 2018	$ 304,289	$ 396	506,169	(195,155)	(9,822)	(1,832)	299,756	4,533
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,743		2,743				2,743
Issuance of common stock through vesting of restricted stock units and option exercises (in shares)		303,441
Issuance of common stock through vesting of restricted stock units and option exercises	47	$ 2	45				47
Employee stock purchase plan (in shares)		267,688
Employee stock purchase plan	1,660	$ 1	1,659				1,660
Repurchases of common stock (in shares)		(39,077)
Repurchases of common stock	(291)				(291)		(291)
Foreign currency translation adjustment	366					340	340	26
Unrealized (loss) on derivative instrument	(742)					(742)	(742)
Net Income (loss)	$ 5,520			5,858			5,858	(338)
Ending balance (in shares) at Mar. 31, 2019	75,907,393	75,907,393
Ending balance at Mar. 31, 2019	$ 313,592	$ 399	$ 510,616	$ (189,297)	$ (10,113)	$ (2,234)	$ 309,371	$ 4,221