Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance, Value at Dec. 31, 2019	$ 47	$ 587,223	$ (400,727)	$ 170	$ 186,713
Balance, Shares at Dec. 31, 2019	46,720,225
Stock-based compensation expense		2,846			2,846
Shares issued upon exercise of stock options, value		75			75
Shares issued upon exercise of stock options, shares	7,500
Net Loss			(28,922)		(28,922)
Other comprehensive loss				(238)	(238)
Balance, Value at Mar. 31, 2020	$ 47	590,144	(429,649)	(68)	160,474
Balance, Shares at Mar. 31, 2020	46,727,725
Balance, Value at Dec. 31, 2020	$ 50	641,195	(392,317)	73	249,001
Balance, Shares at Dec. 31, 2020	49,872,213
Stock-based compensation expense		2,744			2,744
Shares issued upon exercise of stock options, value		688			688
Shares issued upon exercise of stock options, shares	45,035
Shares issued upon vesting of restricted stock units, value		1,388			1,388
Shares issued upon vesting of restricted stock units, shares	109,419
Net Loss			(23,301)		(23,301)
Other comprehensive loss				(61)	(61)
Balance, Value at Mar. 31, 2021	$ 50	$ 646,015	$ (415,618)	$ 12	$ 230,459
Balance, Shares at Mar. 31, 2021	50,026,667