Condensed Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2018	$ 49,456	$ 21	$ 167,040	$ (117,605)
Balance, Shares at Dec. 31, 2018		20,809,025
Issuance of common stock, net of issuance costs	9,446	$ 2	9,444
Issuance of common stock, net of issuance costs, shares		2,632,092
Exercise of common stock options	13		13
Exercise of common stock options, shares		7,039
Issuance of common stock through employee stock purchase plan ("ESPP")	49		49
Issuance of common stock through employee stock purchase plan ("ESPP"), shares		14,009
Stock-based compensation	1,401		1,401
Net loss	(22,692)			(22,692)
Balance at Jun. 30, 2019	37,673	$ 23	177,947	(140,297)
Balance, Shares at Jun. 30, 2019		23,462,165
Balance at Mar. 31, 2019	38,679	$ 21	167,682	(129,024)
Balance, Shares at Mar. 31, 2019		20,816,064
Issuance of common stock, net of issuance costs	9,446	$ 2	9,444
Issuance of common stock, net of issuance costs, shares		2,632,092
Issuance of common stock through employee stock purchase plan ("ESPP")	49		49
Issuance of common stock through employee stock purchase plan ("ESPP"), shares		14,009
Stock-based compensation	772		772
Net loss	(11,273)			(11,273)
Balance at Jun. 30, 2019	37,673	$ 23	177,947	(140,297)
Balance, Shares at Jun. 30, 2019		23,462,165
Balance at Dec. 31, 2019	$ 17,198	$ 25	182,117	(164,944)
Balance, Shares at Dec. 31, 2019	24,735,009	24,735,009
Issuance of common stock, net of issuance costs	$ 13,658	$ 7	13,651
Issuance of common stock, net of issuance costs, shares		7,317,074
Exercise of common stock options	18		18
Exercise of common stock options, shares		11,928
Issuance of common stock through employee stock purchase plan ("ESPP")	27		27
Issuance of common stock through employee stock purchase plan ("ESPP"), shares		20,003
Issuance of common stock through release of restricted stock units ("RSUs"), shares		140,720
Stock-based compensation	2,033		2,033
Net loss	(14,561)			(14,561)
Balance at Jun. 30, 2020	$ 18,373	$ 32	197,846	(179,505)
Balance, Shares at Jun. 30, 2020	32,224,734	32,224,734
Balance at Mar. 31, 2020	$ 10,658	$ 25	183,162	(172,529)
Balance, Shares at Mar. 31, 2020		24,742,146
Issuance of common stock, net of issuance costs	13,658	$ 7	13,651
Issuance of common stock, net of issuance costs, shares		7,317,074
Exercise of common stock options	8		8
Exercise of common stock options, shares		4,791
Issuance of common stock through employee stock purchase plan ("ESPP")	27		27
Issuance of common stock through employee stock purchase plan ("ESPP"), shares		20,003
Issuance of common stock through release of restricted stock units ("RSUs"), shares		140,720
Stock-based compensation	998		998
Net loss	(6,976)			(6,976)
Balance at Jun. 30, 2020	$ 18,373	$ 32	$ 197,846	$ (179,505)
Balance, Shares at Jun. 30, 2020	32,224,734	32,224,734