Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net loss	$ (12,404)	$ (14,088)	$ (27,298)	$ (25,510)
Change in unrealized gain (loss) on short-term investments	(11)	(2)	14	(15)
Comprehensive loss	$ (12,415)	$ (14,090)	$ (27,284)	$ (25,525)