Condensed Consolidated Statement of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (11,537)	$ (10,193)
Unrealized (loss) gain on available-for-sale securities	18	(9)
Comprehensive loss	$ (11,519)	$ (10,202)