Consolidated Statements of Shareholders' Equity - 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, 2016	$ 73,334	$ 50	$ 11	$ 120,985	$ (47,712)
Balance, shares at Dec. 31, 2016		10	10,523
Issuance of common stock, net of issuance costs	29,677	$ 0	$ 1	29,676	0
Issuance of common stock, net of issuance costs, shares		0	831
Exercise of stock options	$ 1,183	$ 0	$ 0	1,183	0
Exercise of stock options, shares	106	0	106
Issuance of restricted common stock	$ 0	$ 0	$ 0	0	0
Issuance of restricted common stock, shares		0	317
Forfeiture of restricted common stock	0	$ 0	$ 0	0	0
Forfeiture of restricted common stock, shares		0	(26)
Purchase and retirement of common stock	(3,030)	$ 0	$ 0	(3,030)	0
Purchase and retirement of common stock, shares		0	(100)
Stock-based compensation	6,954	$ 0	$ 0	6,979	(25)
Net loss	(25,771)	0	0	0	(25,771)
Balance at Dec. 31, 2017	82,347	$ 50	$ 12	155,793	(73,508)
Balance, shares at Dec. 31, 2017		10	11,651
Exercise of stock options	$ 1,256	$ 0	$ 0	1,256	0
Exercise of stock options, shares	102	0	102
Issuance of restricted common stock	$ 0	$ 0	$ 0	0	0
Issuance of restricted common stock, shares		0	239
Forfeiture of restricted common stock	0	$ 0	$ 0	0	0
Forfeiture of restricted common stock, shares		0	(24)
Purchase and retirement of common stock	(2,089)	$ 0	$ 0	(2,089)	0
Purchase and retirement of common stock, shares		0	(77)
Stock-based compensation	7,468	$ 0	$ 0	7,468	0
Cumulative effect of the adoption of the new revenue standard, net of tax	139	0	0	0	139
Net loss	(32,506)	0	0	0	(32,506)
Balance at Dec. 31, 2018	$ 56,615	$ 50	$ 12	$ 162,428	$ (105,875)
Balance, shares at Dec. 31, 2018		10	11,891