CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (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 Comprehensive Income [Abstract]
Net loss	$ (5,037)	$ (14,031)	$ (16,514)	$ (37,169)
Other comprehensive loss:
Net unrealized loss on investments	(36)	(31)	(36)	(14)
Total other comprehensive loss	(36)	(31)	(36)	(14)
Comprehensive loss	$ (5,073)	$ (14,062)	$ (16,550)	$ (37,183)