Summary of significant accounting policies - Liability for Sale of Future Royalties (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Jul. 17, 2020	Jul. 31, 2020	Dec. 31, 2020
Assigned royalty payments
Cash consideration received from Royalty Purchase Agreement	$ 650,000	$ 650,000	$ 650,000
Assigned royalty payment, retained percentage	57.067%
Remaining potential milestones that can be achieved			$ 355,000
Royalty Purchase Agreement
Assigned royalty payments
Cash consideration received from Royalty Purchase Agreement	$ 650,000
Royalty Purchase Agreement \| Assigned Royalty Payments
Assigned royalty payments
Assigned royalty payment, percentage	42.933%
Royalty purchase agreement, termination period	60 days
Royalty purchase agreement, payment maximum	$ 1,300,000