CONDENSED CONSOLIDATED STATEMENTS OF STOCK STOCKHOLDERS' EQUITY (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ 51,561	$ 17	$ 265,926		$ (214,382)
Beginning balance, shares at Dec. 31, 2018		16,782,837
Issuance of common stock warrants	293		293
Issuance of common stock upon exercise of options, shares		268
Issuance of restricted stock	226		226
Issuance of restricted stock, shares		116,580
Stock-based compensation expense	1,903		1,903
Net loss	(12,964)				(12,964)
Ending balance at Mar. 31, 2019	41,019	$ 17	268,348		(227,346)
Ending balance, shares at Mar. 31, 2019		16,899,685
Beginning balance at Dec. 31, 2019	53,739	$ 21	319,115	$ 44	(265,441)
Beginning balance, shares at Dec. 31, 2019		20,851,531
Issuance of common stock upon exercise of options	40		40
Issuance of common stock upon exercise of options, shares		24,687
Issuance of restricted stock	58		58
Issuance of restricted stock, shares		40,931
Stock-based compensation expense	1,447		1,447
Foreign currency translation adjustments	(71)			(71)
Net loss	(13,844)				(13,844)
Ending balance at Mar. 31, 2020	$ 41,369	$ 21	$ 320,660	$ (27)	$ (279,285)
Ending balance, shares at Mar. 31, 2020		20,917,149