Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Collaboration revenue:
Revenues	$ 4,344	$ 2,780
Costs and expenses:
Research and development	37,663	32,771
Selling, general and administrative	18,253	10,814
Total costs and expenses	55,916	43,585
Loss from operations	(51,572)	(40,805)
Other income, net	648	2,772
Loss before income taxes	(50,924)	(38,033)
Income tax provision	(15)	(20)
Net loss	(50,939)	(38,053)
Other comprehensive (loss) income:
Net unrealized holding (losses) gains on short-term and long-term investments during the period, net of tax	(267)	268
Comprehensive loss	$ (51,206)	$ (37,785)
Net loss per share- basic and diluted (in dollars per share)	$ (0.95)	$ (0.74)
Weighted-average number of common shares used in computing net loss per share- basic and diluted (in shares)	53,361	51,126
Cost-sharing, net
Collaboration revenue:
Revenues	$ 2,824	$ 2,780
Royalty
Collaboration revenue:
Revenues	$ 1,520	$ 0