Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2019	$ 68,336	$ 12	$ 326,810	$ 34	$ (258,520)
Balance (in shares) at Dec. 31, 2019		12,040,835
Stock-based compensation expense	805		805
Stock-based compensation expense		7,817
Issuance of common stock from stock grants and option exercises	339		339
Issuance of common stock from stock grants and option exercises, shares		62,969
Issuance of common stock for public offering, net of issuance costs of $2,514 and $3,536	31,986	$ 5	31,981
Issuance of common stock for public offering, net of issuance costs of $2,514 and $3,536, shares		5,307,692
Unrealized gain on available-for-sale debt securities	106			106
Net loss	(4,053)				(4,053)
Balance at Mar. 31, 2020	97,519	$ 17	359,935	140	(262,573)
Balance (in shares) at Mar. 31, 2020		17,419,313
Balance at Dec. 31, 2020	76,069	$ 22	390,803	5	(314,761)
Balance (in shares) at Dec. 31, 2020		22,097,820
Stock-based compensation expense	1,026		1,026
Stock-based compensation expense		10,149
Issuance of common stock for public offering, net of issuance costs of $2,514 and $3,536	49,250	$ 9	49,241
Issuance of common stock for public offering, net of issuance costs of $2,514 and $3,536, shares		9,185,000
Issuance of common stock from stock grants	182		182
Issuance of common stock from stock grants, shares		38,058
Net loss	(22,438)				(22,438)
Balance at Mar. 31, 2021	$ 104,089	$ 31	$ 441,252	$ 5	$ (337,199)
Balance (in shares) at Mar. 31, 2021		31,331,027