CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaboration revenues:
Collaboration revenue	$ 75,589	$ 138,882	$ 109,619
Operating expenses:
Research and development	124,004	149,226	119,880
General and administrative	85,105	82,207	64,466
Other operating expense		0	0
Restructuring		0	0
Total operating expenses	256,916	231,433	184,346
Operating loss	(181,327)	(92,551)	(74,727)
Other income (expense):
Interest income	6,194	4,427	2,226
Other income (expense), net	(928)	28	51,498
Total other income	5,266	4,455	53,724
Net loss	$ (176,061)	$ (88,096)	$ (21,003)
Net loss per share:
Basic and diluted (in dollars per share)	$ (2.26)	$ (1.20)	$ (0.31)
Weighted average shares outstanding:
Basic and diluted (in shares)	77,845	73,136	68,656
Comprehensive loss:
Net loss	$ (176,061)	$ (88,096)	$ (21,003)
Net unrealized holding gains (losses) on available-for-sale marketable securities	53	(226)	82
Comprehensive loss	(176,008)	(88,322)	(20,921)
Product revenue
Collaboration revenues:
Collaboration revenue	39,684	66,803	74,648
Research and development revenue
Collaboration revenues:
Collaboration revenue	$ 35,905	$ 72,079	$ 34,971