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	$ (9,984)	$ (5,894)	$ (20,878)	$ (9,270)
Other comprehensive income (loss):
Unrealized gain (loss) on investments, net of tax	93	120	(63)	(483)
Unrealized (loss) gain on currency translation	0	(1)	1	(2)
Other comprehensive income (loss)	93	119	(62)	(485)
Comprehensive loss	$ (9,891)	$ (5,775)	$ (20,940)	$ (9,755)