CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (71,244)	$ (57,564)	$ (60,585)
Other comprehensive income (loss)
Unrealized gains (losses) on available-for-sale investments, net of taxes	395	(184)	(200)
Comprehensive loss	$ (70,849)	$ (57,748)	$ (60,785)