SHAREHOLDERS’ DEFICIT - USD ($) $ in Thousands	Series D convertible redeemable preferred stock	Initial public offering Common Stock	Initial public offering Additional Paid-In Capital	Initial public offering	Common Stock	Additional Paid-In Capital	Treasury Stock, at cost	Accumulated Deficit	Total
Balance at beginning of year at Dec. 31, 2012					$ 2	$ 11	$ (3)	$ (61,414)	$ (61,404)
Balance at beginning of year (in shares) at Dec. 31, 2012					1,924,845
Increase (decrease) in stockholders' equity (deficit)
Accruals of dividends and accretion to redemption value						(1)		(2,925)	(2,926)
Performance Adjustment of Series A					$ (1)	12,240			12,239
Performance Adjustment of Series A (in shares)					(962,962)
Stock-based compensation expense						62			62
Exercise of common stock options						1			1
Exercise of common stock options (in shares)					1,077
Net loss								(16,197)	(16,197)
Balance at end of year at Dec. 31, 2013					$ 1	12,313	(3)	(80,536)	(68,225)
Balance at end of year (in shares) at Dec. 31, 2013					962,960
Increase (decrease) in stockholders' equity (deficit)
Accruals of dividends and accretion to redemption value								(3,300)	(3,300)
Issuance of restricted stock awards to employees (in shares)					10,869
Stock-based compensation expense						22			22
Exercise of common stock options						72			72
Exercise of common stock options (in shares)					32,390
Net loss								(17,917)	(17,917)
Balance at end of year at Dec. 31, 2014					$ 1	12,407	(3)	(101,753)	(89,348)
Balance at end of year (in shares) at Dec. 31, 2014					1,006,219
Increase (decrease) in stockholders' equity (deficit)
Accruals of dividends and accretion to redemption value						(24,572)			(24,572)
Conversion of preferred stock to common stock	$ (50,000)				$ 13	119,237			119,250
Conversion of preferred stock to common stock (in shares)	(41,666,667)				12,591,463
Issuance of stock, net of issuance costs		$ 7	$ 72,022	$ 72,029		1,052			1,052
Issuance of stock (in shares)		6,670,000			87,662
Extinguishment of prior preferred stock dividends						31,184			31,184
Issuance of restricted stock awards to employees (in shares)					194,694
Stock-based compensation expense						2,209			2,209
Exercise of common stock options						517			517
Exercise of common stock options (in shares)					173,251
Exercise of warrants						6			6
Exercise of warrants (in shares)					16,062
Net loss								(27,255)	(27,255)
Balance at end of year at Dec. 31, 2015					$ 21	$ 214,062	$ (3)	$ (129,008)	$ 85,072
Balance at end of year (in shares) at Dec. 31, 2015					20,739,351