Statements of Convertible Preferred Stock and Shareholders Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock Series A [Member]	Convertible Preferred Stock Series B [Member]	Convertible Preferred Stock Series F [Member]	Financial Advisors [Member]	Common Stock [Member]	Common Stock [Member] Financial Advisors [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Financial Advisors [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2012	$ (69,017)							$ 2,054		$ (71,071)
Beginning balance, shares at Dec. 31, 2012						382,838
Beginning balance at Dec. 31, 2012		$ 30,908	$ 31,074
Beginning balance, shares at Dec. 31, 2012		994,866	2,151,722
Restricted common stock vested in period, value	2							2
Restricted common stock vested in period, shares						540
Issuance of shares from stock options exercised	$ 63							63
Issuance of shares from stock options exercised, shares	20,161					20,161
Beneficial conversion feature related to convertible note	$ 1,123							1,123
Stock-based compensation	423							423
Net loss and comprehensive loss	(18,589)									(18,589)
Ending balance at Dec. 31, 2013	(85,995)							3,665		(89,660)
Ending balance, shares at Dec. 31, 2013						403,539
Ending balance at Dec. 31, 2013		$ 30,908	$ 31,074
Ending balance, shares at Dec. 31, 2013		994,866	2,151,722
Reclassification of stock award liability from equity upon modification	(399)							(399)
Reclassification of stock award liability to equity upon expiration	292							292
Stock-based compensation	820							820
Net loss and comprehensive loss	(24,100)									(24,100)
Ending balance at Dec. 31, 2014	$ (109,382)							4,378		(113,760)
Ending balance, shares at Dec. 31, 2014	403,539					403,539
Ending balance at Dec. 31, 2014	$ 61,982	$ 30,908	$ 31,074
Ending balance, shares at Dec. 31, 2014		994,866	2,151,722
Conversion of convertible notes and accrued interest to common stock	48,222					$ 4		48,218
Conversion of convertible notes and accrued interest to common stock, shares						3,532,756
Conversion of Series A and B convertible preferred stock	61,982	$ (30,908)	$ (31,074)			$ 4		61,978
Conversion of Series A and B convertible preferred stock, shares		(994,866)	(2,151,722)			3,916,772
Issuance of shares in connection with the Merger	21,291			$ 24,832	$ 852	$ 7		21,284	$ 852
Issuance of shares in connection with the Merger, shares				10,000		6,939,282	78,213
Conversion of Series F preferred stock assumed in Merger to common stock	24,832			$ (24,832)				24,832
Conversion of Series F preferred stock assumed in Merger to common stock, shares				(10,000)		222,222
Issuance of shares for cash, value	26,826					$ 3		26,823
Issuance of shares for cash, shares						2,542,365
Issuance of shares at-the-market, value	14,433					$ 1		14,432
Issuance of shares at-the-market, shares						1,141,970
Issuance of shares from stock options exercised	$ 162							162
Issuance of shares from stock options exercised, shares	38,570					38,570
Beneficial conversion feature recognized upon conversion of convertible notes	$ 396							396
Reclassification of warrant liability to additional paid-in capital upon conversion from warrants on convertible preferred stock to common stock	521							521
Stock-based compensation	2,253							2,253
Net loss and comprehensive loss	(49,617)									(49,617)
Ending balance at Dec. 31, 2015	$ 42,771					$ 19		$ 206,129		$ (163,377)
Ending balance, shares at Dec. 31, 2015	18,815,689					18,815,689