Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	ATM Equity Offering Program [Member]	Common Stock [Member]	Common Stock [Member] ATM Equity Offering Program [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] ATM Equity Offering Program [Member]	Accumulated Other Comprehensive Gain (Loss) [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2019	$ 134,344		$ 17		$ 355,291		$ 24	$ (220,988)
Balance, shares at Dec. 31, 2019			36,332,956
Issuance of common stock, net of issuance costs		$ 5,577				$ 5,577
Issuance of common stock, net of issuance costs, shares				568,369
Unrealized loss on marketable securities	(44)						(44)
Lapse of repurchase rights related to common stock issued pursuant to early exercises	8				8
Lapse of repurchase rights related to common stock issued pursuant to early exercises, shares			23,732
Issuance of common stock upon exercise of stock options	91				91
Issuance of common stock upon exercise of stock options, shares			60,682
Stock-based compensation	1,619				1,619
Net income (loss)	(26,206)							(26,206)
Balance at Mar. 31, 2020	115,389		$ 17		362,586		(20)	(247,194)
Balance, shares at Mar. 31, 2020			36,985,739
Balance at Dec. 31, 2019	134,344		$ 17		355,291		24	(220,988)
Balance, shares at Dec. 31, 2019			36,332,956
Issuance of common stock, net of issuance costs, shares		1,160,193
Balance at Dec. 31, 2020	166,739		$ 18		493,023			(326,302)
Balance, shares at Dec. 31, 2020			47,552,693
Offering costs related to the sale of common stock and pre-funded warrants	(451)				(451)
Issuance of common stock under Sales Purchase Agreement, net of issuance costs	20,839				20,839
Issuance of common stock under Sales Purchase Agreement, net of issuance costs, shares			1,169,591
Issuance of common stock, net of issuance costs, shares		0
Unrealized loss on marketable securities	(3)						(3)
Issuance of common stock under employee stock purchase plan (“ESPP”)	279				279
Issuance of common stock under employee stock purchase plan (“ESPP”), shares			109,564
Issuance of common stock upon exercise of stock options	$ 1,824				1,824
Issuance of common stock upon exercise of stock options, shares	365,980		365,980
Stock-based compensation	$ 2,201				2,201
Net income (loss)	7,923							7,923
Balance at Mar. 31, 2021	$ 199,351		$ 18		$ 517,715		$ (3)	$ (318,379)
Balance, shares at Mar. 31, 2021			49,197,828