Condensed Consolidated Statement of Stockholders' Equity - 3 months ended Mar. 31, 2016 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2015	$ 206,007	$ 3	$ 726,651	$ (147)	$ (520,500)
Beginning Balance (in shares) at Dec. 31, 2015	32,466,842	32,466,842
Stock-based compensation	$ 29,510		29,510
Exercises of stock options	$ 222		222
Exercises of stock options (in shares)	26,250	26,250
Unrealized gain on available-for-sale securities	$ 176			176
Net loss	(70,972)				(70,972)
Ending Balance at Mar. 31, 2016	$ 164,943	$ 3	$ 756,383	$ 29	$ (591,472)
Ending Balance (in shares) at Mar. 31, 2016	32,493,092	32,493,092