Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (64,694)	$ (38,844)	$ (117,148)	$ (58,638)
Other comprehensive loss
Unrealized loss on available-for-sale securities	(92)	(71)	(86)	(80)
Comprehensive loss	$ (64,786)	$ (38,915)	$ (117,234)	$ (58,718)