Statement of Stockholders’ Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Common stock, shares issued (in shares)	55,768,414	55,768,414
Balance, beginning of period (in shares) at Dec. 31, 2016	55,768,414
Balance, beginning of period at Dec. 31, 2016	$ 78,581	$ 56	$ 364,148	$ (285,625)	$ 2
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense	$ 1,795		1,795
Exercise of stock options (in shares)	283,995	283,995
Exercise of stock options	$ 355		355
Net issuance of common stock warrant	501		501
Issuance of common stock, net of issuance costs (in shares)		1,081,550
Issuance of common stock, net of issuance costs	6,833	$ 1	6,832
Unrealized gain (loss) on marketable securities	(51)				(51)
Net loss	$ (20,714)			(20,714)
Balance, end of period (in shares) at Mar. 31, 2017	57,133,959	57,133,959
Balance, end of period at Mar. 31, 2017	$ 67,300	$ 57	$ 373,631	$ (306,339)	$ (49)
Common stock, shares issued (in shares)	57,133,959