Condensed Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Net loss	$ (30,726)	$ (18,142)
Other comprehensive loss:
Unrealized loss on available-for-sale securities, net of tax	(28)	(13)
Total comprehensive loss	$ (30,754)	$ (18,155)