Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue:
Collaborative arrangement revenue	$ 115,594	$ 5,740	$ 7,820
Total revenues	250,734	44,674	54,579
Operating expenses:
Research and development	587,956	582,413	448,589
Selling, general and administrative	286,896	271,362	174,129
Cost of royalty and other revenue	5,396	2,978	885
Change in fair value of contingent consideration	(6,468)	2,747	2,999
Total operating expenses	873,780	859,500	626,602
Loss from operations	(623,046)	(814,826)	(572,023)
Interest income, net	11,539	34,761	14,624
Other (expense) income, net	(6,502)	(10,088)	1,961
Loss before income taxes	(618,009)	(790,153)	(555,438)
Income tax (expense) benefit	(686)	545	(187)
Net loss	$ (618,695)	$ (789,608)	$ (555,625)
Net loss per share - basic and diluted (in dollars per share)	$ (9.95)	$ (14.31)	$ (10.68)
Weighted-average number of common shares used in computing net loss per share - basic and diluted (in shares)	62,178	55,191	52,032
Other comprehensive (loss) income:
Other comprehensive income	$ (3,612)	$ 1,734	$ 578
Comprehensive loss	(622,307)	(787,874)	(555,047)
Service revenue
Revenue:
Revenue	114,064	30,729	44,533
Royalty and other revenue
Revenue:
Revenue	$ 21,076	$ 8,205	$ 2,226