Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (14,088)	$ (5,495)	$ (25,510)	$ (12,754)
Unrealized loss on short-term investments	(2)		(15)
Comprehensive loss	$ (14,090)	$ (5,495)	$ (25,525)	$ (12,754)