Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]
Balance at Dec. 31, 2015	$ 51,458	$ 50	$ 9	$ 77,439	$ (26,040)
Balance, shares at Dec. 31, 2015		10	8,919
Exercise of stock options	309	$ 0	$ 0	309	0
Exercise of stock options, shares		0	32
Issuance of restricted common stock	0	$ 0	$ 0	0	0
Issuance of restricted common stock, shares		0	177
Forfeiture of restricted common stock	0	$ 0	$ 0	0	0
Forfeiture of restricted common stock, shares		0	(3)
Purchase and retirement of common stock	(1,104)	$ 0	$ 0	(1,104)	0
Purchase and retirement of common stock, shares		0	(40)
Stock-based compensation	2,782	$ 0	$ 0	2,782	0
Net loss	(10,718)	0	0	0	(10,718)
Balance at Jun. 30, 2016	42,727	$ 50	$ 9	79,426	(36,758)
Balance, shares at Jun. 30, 2016		10	9,085
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	17,702	$ 0	$ 0	17,702	0
Issuance of common stock, net of issuance costs, shares		0	500
Exercise of stock options	$ 568	$ 0	$ 0	568	0
Exercise of stock options, shares	59	0	59
Issuance of restricted common stock	$ 0	$ 0	$ 0	0	0
Issuance of restricted common stock, shares		0	236
Forfeiture of restricted common stock	0	$ 0	$ 0	0	0
Forfeiture of restricted common stock, shares		0	(7)
Purchase and retirement of common stock	(1,348)	$ 0	$ 0	(1,348)	0
Purchase and retirement of common stock, shares		0	(48)
Stock-based compensation	3,191	$ 0	$ 0	3,216	(25)
Net loss	(13,161)	0	0	0	(13,161)
Balance at Jun. 30, 2017	$ 80,286	$ 50	$ 11	$ 141,123	$ (60,898)
Balance, shares at Jun. 30, 2017		10	11,263