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	$ (39,407)	$ (20,102)	$ (23,706)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	16	(25)	31
Comprehensive loss	$ (39,391)	$ (20,127)	$ (23,675)