Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Treasury	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		13,854,205	50,467
Beginning balance at Dec. 31, 2018	$ 44,591	$ 14	$ 0	$ 90,664	$ (13)	$ (46,074)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued during period (in shares)		4,706,700
Issuance of Units in Private Placement, net of offering costs	23,618	$ 5		23,613
Exercise of stock options (in shares)		124
Exercise of stock options	0
Stock-based compensation	754			754
Unrealized gain (loss) on investments	15				15
Unrealized (loss) gain on foreign currency translation	(14)				(14)
Net loss	(12,381)					(12,381)
Ending balance (in shares) at Mar. 31, 2019		18,561,029	50,467
Ending balance at Mar. 31, 2019	56,583	$ 19	$ 0	115,031	(12)	(58,455)
Beginning balance (in shares) at Dec. 31, 2018		13,854,205	50,467
Beginning balance at Dec. 31, 2018	44,591	$ 14	$ 0	90,664	(13)	(46,074)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) on investments	32
Unrealized (loss) gain on foreign currency translation	(10)
Net loss	(24,237)
Ending balance (in shares) at Jun. 30, 2019		18,584,730	50,467
Ending balance at Jun. 30, 2019	45,421	$ 19	$ 0	115,704	9	(70,311)
Beginning balance (in shares) at Mar. 31, 2019		18,561,029	50,467
Beginning balance at Mar. 31, 2019	56,583	$ 19	$ 0	115,031	(12)	(58,455)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Units in Private Placement, net of offering costs	(20)			(20)
Exercise of stock options (in shares)		23,701
Exercise of stock options	11			11
Stock-based compensation	682			682
Unrealized gain (loss) on investments	17				17
Unrealized (loss) gain on foreign currency translation	4				4
Net loss	(11,856)					(11,856)
Ending balance (in shares) at Jun. 30, 2019		18,584,730	50,467
Ending balance at Jun. 30, 2019	45,421	$ 19	$ 0	115,704	9	(70,311)
Beginning balance (in shares) at Dec. 31, 2019		18,587,892	50,467
Beginning balance at Dec. 31, 2019	29,474	$ 19	$ 0	117,371	10	(87,926)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of warrants	60			60
Stock-based compensation	986			986
Unrealized gain (loss) on investments	(15)				(15)
Unrealized (loss) gain on foreign currency translation	(113)				(113)
Net loss	(5,533)					(5,533)
Ending balance (in shares) at Mar. 31, 2020		18,587,892	50,467
Ending balance at Mar. 31, 2020	24,859	$ 19	$ 0	118,417	(118)	(93,459)
Beginning balance (in shares) at Dec. 31, 2019		18,587,892	50,467
Beginning balance at Dec. 31, 2019	29,474	$ 19	$ 0	117,371	10	(87,926)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) on investments	(16)
Unrealized (loss) gain on foreign currency translation	(49)
Net loss	(15,461)
Ending balance (in shares) at Jun. 30, 2020		18,591,231	50,467
Ending balance at Jun. 30, 2020	16,228	$ 19	$ 0	119,651	(55)	(103,387)
Beginning balance (in shares) at Mar. 31, 2020		18,587,892	50,467
Beginning balance at Mar. 31, 2020	24,859	$ 19	$ 0	118,417	(118)	(93,459)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		3,339
Exercise of stock options	2			2
Stock-based compensation	1,232			1,232
Unrealized gain (loss) on investments	(1)				(1)
Unrealized (loss) gain on foreign currency translation	64				64
Net loss	(9,928)					(9,928)
Ending balance (in shares) at Jun. 30, 2020		18,591,231	50,467
Ending balance at Jun. 30, 2020	$ 16,228	$ 19	$ 0	$ 119,651	$ (55)	$ (103,387)