CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (4,898)	$ (5,500)	$ (32,068)	$ (5,060)
Other comprehensive loss:
Change in unrealized (loss) gain on available-for-sale securities, net	(4)	10	(21)	(10)
Other comprehensive (loss) income, net	(4)	10	(21)	(10)
Comprehensive loss	$ (4,902)	$ (5,490)	$ (32,089)	$ (5,070)