Statements of Comprehensive Loss Parenthetical (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Stock-based compensation expense associated with research and development expense	$ 868	$ 940	$ 1,972	$ 2,398
Stock-based compensation expense associated with general and administrative expense	$ 920	$ 900	$ 1,769	$ 1,692