Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Series B Preferred Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series B Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Series B Preferred Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series B Preferred Stock [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Series B Preferred Stock [Member]
Balance at Dec. 31, 2018	$ 56,615		$ 50		$ 12		$ 162,428		$ (105,875)
Balance, shares at Dec. 31, 2018			10		11,891
Issuance of stock, net of issuance costs	19,615		$ 0		$ 0		19,615		0
Issuance of stock, net of issuance costs, shares			0		336
Exercise of stock options	$ 1,178		$ 0		$ 0		1,178		0
Exercise of stock options, shares	55		0		55
Issuance of restricted common stock	$ 0		$ 0		$ 0		0		0
Issuance of restricted common stock, shares			0		300
Forfeiture of restricted common stock	0		$ 0		$ 0		0		0
Forfeiture of restricted common stock, shares			0		(49)
Purchase and retirement of common stock	(3,506)		$ 0		$ 0		(3,506)		0
Purchase and retirement of common stock, shares			0		(87)
Stock-based compensation	8,388		$ 0		$ 0		8,388		0
Net loss	(32,840)		0		0		0		(32,840)
Balance at Dec. 31, 2019	49,450		$ 50		$ 12		188,103		(138,715)
Balance, shares at Dec. 31, 2019			10		12,446
Issuance of stock, net of issuance costs	38,603	$ 16,888	$ 0	$ 17	$ 3	$ 0	38,600	$ 16,871	0	$ 0
Issuance of stock, net of issuance costs, shares			0	17	2,704
Record Series B beneficial conversion feature		11,443		$ 0		0		11,443		0
Accrete Series B beneficial conversion feature		(11,443)		0		0		(11,443)		0
Conversion of Series B preferred stock to common stock		$ 0		$ (17)		$ 1		$ 16		$ 0
Conversion of Series B preferred stock to common stock, shares				(17)		1,198
Exercise of stock options	$ 5,922		$ 0		$ 1		5,921		0
Exercise of stock options, shares	358		0		358
Issuance of restricted common stock	$ 0		$ 0		$ 0		0		0
Issuance of restricted common stock, shares			0		256
Forfeiture of restricted common stock	0		$ 0		$ 0		0		0
Forfeiture of restricted common stock, shares			0		(15)
Purchase and retirement of common stock	(3,760)		$ 0		$ 0		(3,760)		0
Purchase and retirement of common stock, shares			0		(212)
Stock-based compensation	9,273		$ 0		$ 0		9,273		0
Net loss	(32,537)		0		0		0		(32,537)
Balance at Dec. 31, 2020	$ 83,839		$ 50		$ 17		$ 255,024		$ (171,252)
Balance, shares at Dec. 31, 2020			10		16,735