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, 2018	$ 39	$ 428,059	$ (294,354)	$ (114)	$ 133,630
Balance, Shares at Dec. 31, 2018	39,547,558
Stock-based compensation expense		2,234			2,234
Shares issued upon exercise of stock options, Value		234			234
Shares issued upon exercise of stock options, Shares	17,291
Shares issued for consulting services		197			197
Shares issued for consulting services, Shares	10,195
Net loss			(21,960)		(21,960)
Other comprehensive income (loss)				187	187
Balance, Value at Mar. 31, 2019	$ 39	430,724	(316,314)	73	114,522
Balance, Shares at Mar. 31, 2019	39,575,044
Balance, Value at Dec. 31, 2018	$ 39	428,059	(294,354)	(114)	133,630
Balance, Shares at Dec. 31, 2018	39,547,558
Shares issued for consulting services					197
Net loss					(44,920)
Other comprehensive income (loss)					279
Balance, Value at Jun. 30, 2019	$ 40	438,614	(339,274)	165	99,545
Balance, Shares at Jun. 30, 2019	40,027,916
Balance, Value at Mar. 31, 2019	$ 39	430,724	(316,314)	73	114,522
Balance, Shares at Mar. 31, 2019	39,575,044
Stock-based compensation expense		2,681			2,681
Shares issued upon exercise of stock options, Value	$ 1	3,974			3,975
Shares issued upon exercise of stock options, Shares	378,706
Shares issued upon vesting of restricted stock units		1,235			1,235
Shares issued upon vesting of restricted stock units, shares	74,166
Net loss			(22,960)		(22,960)
Other comprehensive income (loss)				92	92
Balance, Value at Jun. 30, 2019	$ 40	438,614	(339,274)	165	99,545
Balance, Shares at Jun. 30, 2019	40,027,916
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 income (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, 2019	$ 47	587,223	(400,727)	170	186,713
Balance, Shares at Dec. 31, 2019	46,720,225
Net loss					(53,990)
Other comprehensive income (loss)					465
Balance, Value at Jun. 30, 2020	$ 47	594,963	(454,717)	635	140,928
Balance, Shares at Jun. 30, 2020	46,864,405
Balance, Value at Mar. 31, 2020	$ 47	590,144	(429,649)	(68)	160,474
Balance, Shares at Mar. 31, 2020	46,727,725
Stock-based compensation expense		2,993			2,993
Shares issued upon exercise of stock options, Value		201			201
Shares issued upon exercise of stock options, Shares	16,846
Shares issued upon vesting of restricted stock units		1,625			1,625
Shares issued upon vesting of restricted stock units, shares	119,834
Net loss			(25,068)		(25,068)
Other comprehensive income (loss)				703	703
Balance, Value at Jun. 30, 2020	$ 47	$ 594,963	$ (454,717)	$ 635	$ 140,928
Balance, Shares at Jun. 30, 2020	46,864,405