Consolidated Statements of Changes in Stockholders' Deficit - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Total	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Accumulated Deficit [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]
Balance at Dec. 31, 2018	$ 25	$ 71,431	$ (61,376)	$ 10,080
Balance (ASU 2014-09 and ASU 2018-07 [Member]) at Dec. 31, 2018					$ 0	$ 20	$ (2,852)	$ (2,832)
Balance (in shares) at Dec. 31, 2018	24,957,309
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Fair value of warrants issued	$ 0	6,800	0	6,800
Common Stock issued upon warrant exercises	$ 1		0	1,821
Common Stock issued upon warrant exercises		1,820
Common Stock issued upon warrant exercises (in shares)	428,571
Common Stock issued upon/under public equity offering	$ 8	37,827	0	37,835
Common Stock issued upon/under public equity offering (in shares)	8,050,000
Costs of public equity offering	$ 0	(540)	0	(540)
Shares issued under employee stock purchase plan	$ 0	237	0	237
Shares issued under employee stock purchase plan (in shares)	56,378
Vested restricted stock units	$ 0	(313)	0	(313)
Vested restricted stock units (in shares)	70,627
Share-based compensation expense	$ 0	7,036	0	7,036
Share-based compensation expense (in shares)	0
Net loss	$ 0	0	(66,246)	(66,246)
Balance at Dec. 31, 2019	$ 34	124,318	(130,474)	(6,122)
Balance (in shares) at Dec. 31, 2019	33,562,885
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Fair value of warrants issued	$ 0	735	0	735
Common Stock issued upon warrant exercises (in shares)	428,571
Common Stock issued upon/under public equity offering	$ 1	6,527	0	6,528
Common Stock issued upon/under public equity offering (in shares)	930,933
Costs of common stock issuance under public equity offering	$ 0	(473)	0	(473)
Costs of common stock issuance under public equity offering (in shares)	0
Shares issued under employee stock purchase plan	$ 0	158	0	158
Shares issued under employee stock purchase plan (in shares)	32,986
Exercise of stock options	$ 0	2	0	2
Exercise of stock options (in shares)	500
Vested restricted stock units	$ 0	(99)	0	(99)
Vested restricted stock units (in shares)	41,950
Share-based compensation expense	$ 0	6,557	0	6,557
Share-based compensation expense (in shares)	0
Net loss	$ 0	0	(55,783)	(55,783)
Balance at Dec. 31, 2020	$ 35	$ 137,725	$ (186,257)	$ (48,497)
Balance (in shares) at Dec. 31, 2020	34,569,254