Stock-Based Compensation (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	$ 1,086	$ 491	$ 3,386	$ 1,110
General and administrative
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	593	276	1,628	575
Research and development
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	$ 493	$ 215	$ 1,758	$ 535