Consolidated Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (13,313)	$ (4,537)	$ (45,381)	$ (9,597)
Other comprehensive loss:
Change in unrealized gain (loss) on available-for-sale securities, net	6	(9)	(15)	(19)
Other comprehensive income (loss), net	6	(9)	(15)	(19)
Comprehensive loss	$ (13,307)	$ (4,546)	$ (45,396)	$ (9,616)