Collaboration and Other Agreements - Zai Lab (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Nov. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Collaboration And Other Agreements [Line Items]
Revenues		$ 13,682	$ 9,662
Deferred revenue, current		9,506		$ 10,700
Zai Lab Agreement \| Zai Labs
Collaboration And Other Agreements [Line Items]
Non-refundable upfront payment	$ 25,000
Non-refundable upfront payment, net of tax withholding	22,500
Nonrefundable payment tax withholding	$ 2,500
Potential development and regulatory milestone payments under agreement		140,000
Revenues		4,000	$ 4,000
Revenues, Net Of Tax Withholding		3,600
Revenues, Tax Withholding		400
Deferred revenue, current		5,000		$ 5,000
Zai Lab Clinical Supply Agreements \| Zai Labs
Collaboration And Other Agreements [Line Items]
Revenues		$ 1,000
Zai Lab Agreement, Margetuximab \| Zai Labs \| Maximum
Collaboration And Other Agreements [Line Items]
Potential proceeds from royalties (percent)	20.00%
Zai Lab Agreement, TRIDENT molecule \| Zai Labs
Collaboration And Other Agreements [Line Items]
Potential proceeds from royalties (percent)	10.00%