Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net loss	$ (12,148)	$ (7,700)	$ (37,658)	$ (20,454)
Unrealized gain (loss) on short-term investments	(28)	5	(43)	5
Comprehensive loss	$ (12,176)	$ (7,695)	$ (37,701)	$ (20,449)