License agreements - Zai Lab (Details) - Zai Lab Ltd - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Aug. 31, 2019	Mar. 31, 2020
Upfront and immediate milestone payment to be received under license agreement	$ 17.5
Research and development expenses reimbursed		$ 0.2
Reimbursable costs included in accounts receivable		$ 0.2
Development Regulatory And Commercial Milestones
Upfront payment under license agreement	$ 37.5