Consolidated Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (29,281)	$ (17,708)	$ (10,932)
Other comprehensive income:
Unrealized gain on short-term investments	22
Comprehensive loss	$ (29,259)	$ (17,708)	$ (10,932)