STATEMENT OF STOCKHOLDERS' EQUITY - 3 months ended Mar. 31, 2016 - USD ($) $ in Thousands	Total	Stock Options	Common Stock	Common Stock Stock Options	Additional Paid-in Capital Common Stock	Additional Paid-in Capital Common Stock Stock Options	Accumulated Deficit
Beginning Balance (in shares) at Dec. 31, 2015			131,718,579
Beginning Balance at Dec. 31, 2015	$ 87,371		$ 132		$ 579,939		$ (492,700)
Stock-based compensation	$ 2,009				2,009
Exercise of employee stock options (in shares)	93,672			84,462
Exercise of employee stock options		$ 367				$ 367
Repurchase of common stock (in shares)			(168)
Repurchase of common stock	$ (2)				(2)
Issuance of common stock in a license agreement	87				87
Net loss	(12,019)						(12,019)
Ending Balance (in shares) at Mar. 31, 2016			131,802,873
Ending Balance at Mar. 31, 2016	$ 77,813		$ 132		$ 582,400		$ (504,719)