Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [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 common stock, net of issuance costs	19,615	$ 0	$ 0	19,615	0
Issuance of common stock, net of issuance costs, shares		0	336
Exercise of stock options	293	$ 0	$ 0	293	0
Exercise of stock options, shares		0	23
Issuance of restricted common stock	0	$ 0	$ 0	0	0
Issuance of restricted common stock, shares		0	273
Forfeiture of restricted common stock	0	$ 0	$ 0	0	0
Forfeiture of restricted common stock, shares		0	(46)
Purchase and retirement of common stock	(1,868)	$ 0	$ 0	(1,868)	0
Purchase and retirement of common stock, shares		0	(44)
Stock-based compensation	4,143	$ 0	$ 0	4,143	0
Net loss	(16,396)	0	0	0	(16,396)
Balance at Jun. 30, 2019	62,402	$ 50	$ 12	184,611	(122,271)
Balance, shares at Jun. 30, 2019		10	12,433
Balance at Mar. 31, 2019	49,843	$ 50	$ 12	164,119	(114,338)
Balance, shares at Mar. 31, 2019		10	12,135
Issuance of common stock, net of issuance costs	19,615	$ 0	$ 0	19,615	0
Issuance of common stock, net of issuance costs, shares		0	336
Exercise of stock options	194	$ 0	$ 0	194	0
Exercise of stock options, shares		0	13
Issuance of restricted common stock	0	$ 0	$ 0	0	0
Issuance of restricted common stock, shares		0	18
Forfeiture of restricted common stock	0	$ 0	$ 0	0	0
Forfeiture of restricted common stock, shares		0	(45)
Purchase and retirement of common stock	(1,382)	$ 0	$ 0	(1,382)	0
Purchase and retirement of common stock, shares		0	(24)
Stock-based compensation	2,065	$ 0	$ 0	2,065	0
Net loss	(7,933)	0	0	0	(7,933)
Balance at Jun. 30, 2019	62,402	$ 50	$ 12	184,611	(122,271)
Balance, shares at Jun. 30, 2019		10	12,433
Balance at Dec. 31, 2019	49,450	$ 50	$ 12	188,103	(138,715)
Balance, shares at Dec. 31, 2019		10	12,446
Issuance of common stock, net of issuance costs	574	$ 0	$ 1	573	0
Issuance of common stock, net of issuance costs, shares		0	28
Exercise of stock options	$ 135	$ 0	$ 0	135	0
Exercise of stock options, shares	8	0	8
Issuance of restricted common stock	$ 0	$ 0	$ 0	0	0
Issuance of restricted common stock, shares		0	229
Forfeiture of restricted common stock	0	$ 0	$ 0	0	0
Forfeiture of restricted common stock, shares		0	(4)
Purchase and retirement of common stock	(1,120)	$ 0	$ 0	(1,120)	0
Purchase and retirement of common stock, shares		0	(48)
Stock-based compensation	4,607	$ 0	$ 0	4,607	0
Net loss	(16,369)	0	0	0	(16,369)
Balance at Jun. 30, 2020	37,277	$ 50	$ 13	192,298	(155,084)
Balance, shares at Jun. 30, 2020		10	12,659
Balance at Mar. 31, 2020	$ 42,743	$ 50	$ 13	190,303	(147,623)
Balance, shares at Mar. 31, 2020		10	12,645
Exercise of stock options, shares	0
Issuance of restricted common stock	$ 0	$ 0	$ 0	0	0
Issuance of restricted common stock, shares		0	43
Forfeiture of restricted common stock	0	$ 0	$ 0	0	0
Forfeiture of restricted common stock, shares		0	(4)
Purchase and retirement of common stock	(382)	$ 0	$ 0	(382)	0
Purchase and retirement of common stock, shares		0	(25)
Stock-based compensation	2,377	$ 0	$ 0	2,377	0
Net loss	(7,461)	0	0	0	(7,461)
Balance at Jun. 30, 2020	$ 37,277	$ 50	$ 13	$ 192,298	$ (155,084)
Balance, shares at Jun. 30, 2020		10	12,659