Condensed 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
Net loss	$ (31,350)	$ (21,598)	$ (62,076)	$ (39,741)
Other comprehensive loss:
Unrealized loss on available-for-sale securities, net of tax	(5)	(56)	(33)	(69)
Total comprehensive loss	$ (31,355)	$ (21,654)	$ (62,109)	$ (39,810)