Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated deficit
Balance at Dec. 31, 2014	$ 30,409	$ 41	$ 143,086	$ (112,718)
Balance (shares) at Dec. 31, 2014		40,856,815
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares	15,872	$ 3	15,869
Issuance of shares (in shares)		2,974,136
Stock-based compensation expense	2,038		2,038
Exercise of stock options	$ 255		255
Exercise of stock options (in shares)	56,250	56,250
Exercise of warrants	$ 82		82
Exercise of warrants (in shares)		11,584
Net loss	(34,453)			(34,453)
Balance at Dec. 31, 2015	14,203	$ 44	161,330	(147,171)
Balance (shares) at Dec. 31, 2015		43,898,785
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect from adoption of new accounting standard			100	(100)
Issuance of shares (in shares)		159,841
Intrinsic value of beneficial conversion feature, net of issuance costs	7,017		7,017
Stock-based compensation expense	$ 1,933		1,933
Exercise of stock options (in shares)	0
Net loss	$ (15,292)			(15,292)
Balance at Dec. 31, 2016	$ 7,861	$ 44	$ 170,380	$ (162,563)
Balance (shares) at Dec. 31, 2016		44,058,626