License agreements - Innovent (Details) - Innovent - USD ($) $ in Millions	1 Months Ended		6 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Jun. 30, 2019
License agreements
Upfront and immediate milestone payment to be received under license agreement	$ 40.0
Regulatory Milestones
License agreements
Milestone payment made under license agreement			$ 20.0
Regulatory Milestones | Maximum
License agreements
Upfront and immediate milestone payment to be received under license agreement		$ 20.0
Development and Regulatory Milestones | Maximum
License agreements
Upfront and immediate milestone payment to be received under license agreement		129.0
Commercialization Milestones | Maximum
License agreements
Upfront and immediate milestone payment to be received under license agreement		$ 202.5