CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Non- Controlling Interest
Beginning Balances (in shares) at Dec. 31, 2018		102,187,471
Beginning Balances at Dec. 31, 2018	$ 367,257	$ 1,022	$ 929,632	$ (562,696)	$ (1,440)	$ 739
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax (in shares)		141,281
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	216	$ 1	215
Issuance costs related to public offering	(258)		(258)
Stock-based compensation	4,523		4,523
Foreign currency translation adjustment	(1,504)				(1,504)
Net unrealized gain (loss) on marketable securities	253				253
Net loss	(42,203)			(42,150)		(53)
Ending Balances (in shares) at Mar. 31, 2019		102,328,752
Ending Balances at Mar. 31, 2019	329,181	$ 1,023	934,112	(603,949)	(2,691)	686
Beginning Balances (in shares) at Dec. 31, 2019		115,972,708
Beginning Balances at Dec. 31, 2019	432,739	$ 1,160	1,090,828	(656,985)	(2,449)	185
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax (in shares)		305,845
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	409	$ 3	406
Stock-based compensation	5,620		5,620
Foreign currency translation adjustment	(1,633)				(1,633)
Net unrealized gain (loss) on marketable securities	254				254
Net loss	(42,974)			(42,913)		(61)
Ending Balances (in shares) at Mar. 31, 2020		116,278,553
Ending Balances at Mar. 31, 2020	$ 394,415	$ 1,163	$ 1,096,854	$ (699,898)	$ (3,828)	$ 124