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, 2014	$ 52,174	$ 50	$ 8	$ 60,222	$ (8,106)
Balance, shares at Dec. 31, 2014		10	8,427
Issuance of common stock, net of issuance costs	12,896		$ 1	12,895
Issuance of common stock, net of issuance costs, shares			342
Exercise of stock options	1,321			1,321
Exercise of stock options, shares			91
Issuance of restricted common stock, shares			132
Forfeiture of restricted common stock, shares			(29)
Purchase and retirement of common stock	(1,833)			(1,833)
Purchase and retirement of common stock, shares			(57)
Stock-based compensation	3,994			3,994
Net loss	(12,631)				(12,631)
Balance at Sep. 30, 2015	55,921	$ 50	$ 9	76,599	(20,737)
Balance, shares at Sep. 30, 2015		10	8,906
Balance at Dec. 31, 2015	51,458	$ 50	$ 9	77,439	(26,040)
Balance, shares at Dec. 31, 2015		10	8,919
Issuance of common stock, net of issuance costs	39,700		$ 2	39,698
Issuance of common stock, net of issuance costs, shares			1,418
Exercise of stock options	$ 476			476
Exercise of stock options, shares	49		49
Issuance of restricted common stock, shares			191
Forfeiture of restricted common stock, shares			(7)
Purchase and retirement of common stock	$ (1,879)			(1,879)
Purchase and retirement of common stock, shares			(61)
Stock-based compensation	4,283			4,283
Net loss	(15,916)				(15,916)
Balance at Sep. 30, 2016	$ 78,122	$ 50	$ 11	$ 120,017	$ (41,956)
Balance, shares at Sep. 30, 2016		10	10,509