Condensed Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Total	IPO [Member]	Common Stock [Member]	Common Stock [Member] IPO [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] IPO [Member]	Accumulated Deficit [Member]
Balances at beginning at Dec. 31, 2018	$ 30,413		$ 32		$ 157,413		$ (127,032)
Balances at beginning (shares) at Dec. 31, 2018			31,755,169
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	248				248
Issuance of common stock under equity incentive plan (shares)			21,415
Net loss	(7,030)						(7,030)
Balances at ending at Mar. 31, 2019	23,631		$ 32		157,661		(134,062)
Balances at end (shares) at Mar. 31, 2019			31,776,584
Balances at beginning at Dec. 31, 2018	30,413		$ 32		157,413		(127,032)
Balances at beginning (shares) at Dec. 31, 2018			31,755,169
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(16,149)
Balances at ending at Sep. 30, 2019	14,885		$ 32		158,034		(143,181)
Balances at end (shares) at Sep. 30, 2019			31,793,292
Balances at beginning at Mar. 31, 2019	23,631		$ 32		157,661		(134,062)
Balances at beginning (shares) at Mar. 31, 2019			31,776,584
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	220				220
Issuance of common stock under equity incentive plan (shares)			16,708
Net loss	(10,008)						(10,008)
Balances at ending at Jun. 30, 2019	13,843		$ 32		157,881		(144,070)
Balances at end (shares) at Jun. 30, 2019			31,793,292
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	153				153
Net loss	889						889
Balances at ending at Sep. 30, 2019	14,885		$ 32		158,034		(143,181)
Balances at end (shares) at Sep. 30, 2019			31,793,292
Balances at beginning at Dec. 31, 2019	14,947		$ 45		172,708		(157,806)
Balances at beginning (shares) at Dec. 31, 2019			44,658,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	392				392
Issuance of common stock under equity incentive plan (shares)			28,757
Net loss	(5,858)						(5,858)
Balances at ending at Mar. 31, 2020	9,481		$ 45		173,100		(163,664)
Balances at end (shares) at Mar. 31, 2020			44,686,811
Balances at beginning at Dec. 31, 2019	14,947		$ 45		172,708		(157,806)
Balances at beginning (shares) at Dec. 31, 2019			44,658,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(21,787)
Balances at ending at Sep. 30, 2020	48,006		$ 80		227,519		(179,593)
Balances at end (shares) at Sep. 30, 2020			79,593,621
Balances at beginning at Mar. 31, 2020	9,481		$ 45		173,100		(163,664)
Balances at beginning (shares) at Mar. 31, 2020			44,686,811
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	341				341
Issuance of common stock under equity incentive plan	17				17
Issuance of common stock under equity incentive plan (shares)			24,979
Sale of common stock in public offering, net of costs of $3,778		$ 53,722		$ 35		$ 53,687
Sale of common stock in public offering, net of costs, (shares)				34,848,484
Net loss	(7,384)						(7,384)
Balances at ending at Jun. 30, 2020	56,177		$ 80		227,145		(171,048)
Balances at end (shares) at Jun. 30, 2020			79,560,274
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	374				374
Issuance of common stock under equity incentive plan (shares)			33,347
Net loss	(8,545)						(8,545)
Balances at ending at Sep. 30, 2020	$ 48,006		$ 80		$ 227,519		$ (179,593)
Balances at end (shares) at Sep. 30, 2020			79,593,621