Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (153,524)	$ (81,177)	$ (53,916)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments, net of tax	79	(226)	(95)
Net foreign currency translation loss	(272)	(377)	(291)
Other comprehensive loss, net of tax	(193)	(603)	(386)
Comprehensive loss	$ (153,717)	$ (81,780)	$ (54,302)