CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Follow-on Public Offering, One Common Stock	Follow-on Public Offering, One Additional Paid-in Capital	Follow-on Public Offering, One	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, 2019					$ 22	$ 295,121			$ (235,574)	$ 59,569
Balance (in shares) at Dec. 31, 2019					21,625,088		7,307
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)					59,978
Issuance of restricted stock (in shares)					5,250
Deemed dividend on beneficial conversion feature - Series A convertible preferred stock						8,880			(8,880)
Unrealized gain (loss) on investments								$ 27		27
Net loss									(18,672)	(18,672)
Balance at Mar. 31, 2020					$ 22	306,189		27	(263,126)	43,112
Balance (in shares) at Mar. 31, 2020					21,690,316		7,307
Balance at Dec. 31, 2019					$ 22	295,121			(235,574)	59,569
Balance (in shares) at Dec. 31, 2019					21,625,088		7,307
Increase (Decrease) in Stockholders' Equity (Deficit)
Net loss										(34,347)
Balance at Jun. 30, 2020				$ 8,745	$ 31	371,143		27	(278,801)	101,145
Balance (in shares) at Jun. 30, 2020				9,303	30,555,978		7,307
Balance at Mar. 31, 2020					$ 22	306,189		27	(263,126)	43,112
Balance (in shares) at Mar. 31, 2020					21,690,316		7,307
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense						1,796				1,796
Exercise of stock options						200				200
Exercise of stock options (in shares)					47,455
Issuance of common stock	$ 5	$ 42,905	$ 42,910
Issuance of common stock (in shares)	4,600,000
Issuance of common stock under equity distribution agreement						602				602
Issuance of common stock under equity distribution agreement (in shares)					78,807
Transfer of convertible preferred stock into permanent equity				$ 8,745						8,745
Transfer of convertible preferred stock into permanent equity (in shares)				9,303
Conversion of convertible preferred stock to common stock					$ 4	19,451				19,455
Conversion of convertible preferred stock to common stock (in shares)					4,139,400
Net loss									(15,675)	(15,675)
Balance at Jun. 30, 2020				$ 8,745	$ 31	371,143		$ 27	(278,801)	101,145
Balance (in shares) at Jun. 30, 2020				9,303	30,555,978		7,307
Balance at Dec. 31, 2020				$ 4,469	$ 37	444,622			(311,929)	137,199
Balance (in shares) at Dec. 31, 2020				4,753	36,585,767		7,307
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense						5,035				5,035
Exercise of stock options						244				244
Exercise of stock options (in shares)					55,030
Financing costs under equity distribution agreement						(3)				(3)
Net loss									(27,141)	(27,141)
Balance at Mar. 31, 2021				$ 4,469	$ 37	449,898			(339,070)	115,334
Balance (in shares) at Mar. 31, 2021				4,753	36,640,797		7,307
Balance at Dec. 31, 2020				$ 4,469	$ 37	444,622			(311,929)	137,199
Balance (in shares) at Dec. 31, 2020				4,753	36,585,767		7,307
Increase (Decrease) in Stockholders' Equity (Deficit)
Net loss										(50,964)
Balance at Jun. 30, 2021				$ 4,302	$ 37	453,613			(362,893)	95,059
Balance (in shares) at Jun. 30, 2021				4,575	36,739,709		7,307
Balance at Mar. 31, 2021				$ 4,469	$ 37	449,898			(339,070)	115,334
Balance (in shares) at Mar. 31, 2021				4,753	36,640,797		7,307
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense						2,991				2,991
Exercise of stock options						557				557
Exercise of stock options (in shares)					63,312
Conversion of convertible preferred stock to common stock				$ (167)		167
Conversion of convertible preferred stock to common stock (in shares)				(178)	35,600
Net loss									(23,823)	(23,823)
Balance at Jun. 30, 2021				$ 4,302	$ 37	$ 453,613			$ (362,893)	$ 95,059
Balance (in shares) at Jun. 30, 2021				4,575	36,739,709		7,307