CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]
Balance at Dec. 31, 2019	$ 8,330	$ 11	$ 472,765	$ (465,286)	$ 840
Balance, shares at Dec. 31, 2019		10,941,659
Net loss	(26,124)			(26,124)
Issuance of stock, net of issue costs	19,990	$ 15	19,975
Issuance of stock, net of issue costs, shares		1,500,000
Employee stock purchase plan	187	$ 1	186
Employee stock purchase plan, shares		16,166
Vesting of stock units	(90)		(90)
Vesting of stock units, shares		61,888
Stock-based compensation	1,895		1,895
Balance at Jun. 30, 2020	4,188	$ 27	494,731	(491,410)	840
Balance, shares at Jun. 30, 2020		12,519,713
Balance at Mar. 31, 2020	16,474	$ 27	494,067	(478,460)	840
Balance, shares at Mar. 31, 2020		12,474,110
Net loss	(12,950)			(12,950)
Vesting of stock units	(71)		(71)
Vesting of stock units, shares		45,603
Stock-based compensation	735		735
Balance at Jun. 30, 2020	4,188	$ 27	494,731	(491,410)	840
Balance, shares at Jun. 30, 2020		12,519,713
Balance at Dec. 31, 2020	$ 18,541	$ 18	528,362	(510,680)	841
Balance, shares at Dec. 31, 2020	18,139,981	18,139,981
Net loss	$ (22,290)			(22,290)
Issuance of stock, net of issue costs	108,403	$ 11	108,392
Issuance of stock, net of issue costs, shares		10,513,538
Employee stock purchase plan	173		173
Employee stock purchase plan, shares		27,713
Exercise of stock options	10		10
Exercise of stock options, shares		827
Vesting of stock units	(140)		(140)
Vesting of stock units, shares		72,133
Stock-based compensation	2,168		2,168
Balance at Jun. 30, 2021	$ 106,865	$ 29	638,965	(532,970)	841
Balance, shares at Jun. 30, 2021	28,754,192	28,754,192
Balance at Mar. 31, 2021	$ 115,707	$ 29	637,797	(522,960)	841
Balance, shares at Mar. 31, 2021		28,741,475
Net loss	(10,010)			(10,010)
Vesting of stock units	(12)		(12)
Vesting of stock units, shares		12,717
Stock-based compensation	1,180		1,180
Balance at Jun. 30, 2021	$ 106,865	$ 29	$ 638,965	$ (532,970)	$ 841
Balance, shares at Jun. 30, 2021	28,754,192	28,754,192