Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - 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	$ (55,158)	$ (35,793)	$ (160,399)	$ (97,869)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	111	(46)	259	(79)
Total comprehensive loss	$ (55,047)	$ (35,839)	$ (160,140)	$ (97,948)