Significant agreements - Jazz Pharmaceuticals (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Significant agreements
Collaboration revenues		$ 614	$ 1,610	$ 8,520	$ 6,079
Material transfer agreement
Significant agreements
Upfront cash payment	$ 1,000
Threshold period for receipt of revenue after receipt of the materials and related data package	30 days
Term (in years)	14 months
Threshold period of notice required for termination of agreement	45 days
Collaboration revenues		$ 0	$ 0	$ 1,000	$ 0