STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Series A Convertible Preferred Stock Preferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income	Accumulated Deficit	Total
Balance at Dec. 31, 2018		$ 53	$ 249,727		$ (2)	$ (181,453)	$ 68,325
Balance (in shares) at Dec. 31, 2018		52,548,244		29,231
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense			1,836				1,836
Exercise of stock options			65				65
Exercise of stock options (in shares)		55,812
Forfeiture of restricted stock (in shares)		(20,200)
Unrealized gain on investments					2		2
Net loss						(12,483)	(12,483)
Balance at Mar. 31, 2019		$ 53	251,628			(193,936)	57,745
Balance (in shares) at Mar. 31, 2019		52,583,856		29,231
Balance at Dec. 31, 2018		$ 53	249,727		(2)	(181,453)	68,325
Balance (in shares) at Dec. 31, 2018		52,548,244		29,231
Increase (Decrease) in Stockholders' Equity (Deficit)
Net loss							(24,906)
Balance at Jun. 30, 2019		$ 53	252,891			(206,359)	46,585
Balance (in shares) at Jun. 30, 2019		52,583,856		29,231
Balance at Mar. 31, 2019		$ 53	251,628			(193,936)	57,745
Balance (in shares) at Mar. 31, 2019		52,583,856		29,231
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense			1,263				1,263
Net loss						(12,423)	(12,423)
Balance at Jun. 30, 2019		$ 53	252,891			(206,359)	46,585
Balance (in shares) at Jun. 30, 2019		52,583,856		29,231
Balance at Dec. 31, 2019		$ 87	295,056			(235,574)	59,569
Balance (in shares) at Dec. 31, 2019		86,500,353		29,231
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense			1,876				1,876
Exercise of stock options			312				312
Exercise of stock options (in shares)		239,913
Issuance of restricted stock (in shares)		21,000
Unrealized gain on investments					27		27
Deemed dividend on beneficial conversion feature - Series A convertible preferred stock			8,880			(8,880)
Net loss						(18,672)	(18,672)
Balance at Mar. 31, 2020		$ 87	306,124		27	(263,126)	43,112
Balance (in shares) at Mar. 31, 2020		86,761,266		29,231
Balance at Dec. 31, 2019		$ 87	295,056			(235,574)	59,569
Balance (in shares) at Dec. 31, 2019		86,500,353		29,231
Increase (Decrease) in Stockholders' Equity (Deficit)
Net loss							(34,347)
Balance at Jun. 30, 2020	$ 8,745	$ 123	371,051		27	(278,801)	101,145
Balance (in shares) at Jun. 30, 2020	9,303	122,223,914		29,231
Balance at Mar. 31, 2020		$ 87	306,124		27	(263,126)	43,112
Balance (in shares) at Mar. 31, 2020		86,761,266		29,231
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense			1,796				1,796
Issuance of common stock under equity distribution agreement			602				602
Issuance of common stock under equity distribution agreement (in shares)		315,229
Issuance of stock		$ 19	42,891				42,910
Issuance of stock (in shares)		18,400,000
Exercise of stock options			200				200
Exercise of stock options (in shares)		189,819
Conversion of convertible preferred stock to common stock		$ 17	19,438				19,455
Conversion of convertible preferred stock to common stock (in shares)		16,557,600
Transfer of convertible preferred stock into permanent equity	$ 8,745						8,745
Transfer of convertible preferred stock into permanent equity (in shares)	9,303
Net loss						(15,675)	(15,675)
Balance at Jun. 30, 2020	$ 8,745	$ 123	$ 371,051		$ 27	$ (278,801)	$ 101,145
Balance (in shares) at Jun. 30, 2020	9,303	122,223,914		29,231