Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (20,092)	$ (16,682)	$ (38,475)	$ (34,567)
Other comprehensive income, net of income taxes:
Net unrealized gains on available-for-sale securities	29	122	5	183
Reclassification of net realized gains on available-for-sale securities included in net loss	(1)	0	0	0
Total other comprehensive income	28	122	5	183
Comprehensive loss	$ (20,064)	$ (16,560)	$ (38,470)	$ (34,384)