Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Collaboration revenue:
Collaboration revenue from customers	$ 3,552	$ 4,111
Other collaboration revenue	52	94
Total collaboration revenue	3,604	4,205
Operating expenses:
Research and development	51,016	37,403
General and administrative	12,555	9,310
Total operating expenses	63,571	46,713
Loss from operations	(59,967)	(42,508)
Interest and other income, net	3,069	3,516
Loss before income taxes	(56,898)	(38,992)
Income tax benefit	135	0
Net loss	(56,763)	(38,992)
Other comprehensive income (loss):
Net unrealized gain on marketable securities, net of tax	485	981
Comprehensive loss	$ (56,278)	$ (38,011)
Net loss per share, basic and diluted (usd per share)	$ (0.55)	$ (0.41)
Weighted average number of shares outstanding, basic and diluted (in shares)	102,419,718	94,984,503