Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (54,568)	$ (50,378)	$ (29,740)
Other comprehensive income (loss):
Net change in unrealized gains (losses) on available-for-sale securities	98	49	(56)
Comprehensive loss	(54,470)	(50,329)	(29,796)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	$ 98	$ 49	$ (56)