Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (60,417)	$ (35,844)	$ (177,565)	$ (94,482)
Other comprehensive loss
Unrealized gain (loss) on available-for-sale securities	149	(41)	63	(121)
Comprehensive loss	$ (60,268)	$ (35,885)	$ (177,502)	$ (94,603)