Condensed Consolidated Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (11,422)	$ (7,259)
Unrealized loss on short-term investments	(13)
Comprehensive loss	$ (11,435)	$ (7,259)