Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaboration revenue:
Revenues	$ 22,561	$ 4,208	$ 66,656	$ 34,655
Costs and expenses:
Research and development	40,747	37,630	116,663	105,125
Selling, general and administrative	21,042	15,501	59,705	40,394
Total costs and expenses	61,789	53,131	176,368	145,519
Loss from operations	(39,228)	(48,923)	(109,712)	(110,864)
Other (expense), income net	(6)	3,520	1,108	9,523
Loss before income taxes	(39,234)	(45,403)	(108,604)	(101,341)
Income tax (provision) benefit	(11)	34	(31)	58
Net loss	(39,245)	(45,369)	(108,635)	(101,283)
Other comprehensive (loss) income:
Net unrealized holding (losses) gains on short-term and long-term investments during the period, net of tax	(142)	(29)	(248)	691
Comprehensive loss	$ (39,387)	$ (45,398)	$ (108,883)	$ (100,592)
Net loss per share- basic and diluted (in dollars per share)	$ (0.66)	$ (0.86)	$ (1.95)	$ (1.94)
Weighted-average number of common shares used in computing net loss per share- basic and diluted (in shares)	59,640	52,882	55,635	52,239
Milestone
Collaboration revenue:
Revenues	$ 0	$ 0	$ 25,000	$ 25,000
Cost-sharing, net
Collaboration revenue:
Revenues	3,298	4,208	9,800	9,655
Royalty
Collaboration revenue:
Revenues	$ 19,263	$ 0	$ 31,856	$ 0