CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (18,598)	$ (16,863)
Other comprehensive loss:
Unrealized losses on available-for-sale investments, net of taxes of zero and ($2,058) for the three months ended March 31, 2017 and 2016, respectively	(246)	(3,922)
Comprehensive loss	$ (18,844)	$ (20,785)