Collaboration agreements - Merck Dolaflexin Agreement (Details)	1 Months Ended	3 Months Ended		60 Months Ended
	Jun. 30, 2014 USD ($) target	Mar. 31, 2023 USD ($) target	Mar. 31, 2022 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2017 target
Collaboration agreements
Collaboration revenue		$ 7,802,000	$ 2,036,000
Deferred revenue		$ 144,351,000	42,198,000		$ 147,653,000	$ 3,944,000
2014 Merck KGaA
Collaboration agreements
Upfront payment received	$ 12,000,000
Number of targets designated | target	6	6					6
Amount of additional fees receivable when target is designated and commercial license to target is granted	$ 0
Development milestones		$ 0	0	$ 3,000,000
Number of targets with satisfied performance obligations | target		4
2018 Merck KGaA
Collaboration agreements
Collaboration revenue		$ 0	$ 0
2014 & 2018 Collaboration and Commercial License Agreement and Supply Agreement Merck KGaA
Collaboration agreements
Deferred revenue		$ 3,900,000			$ 3,900,000
Rights to Future Technological Improvements | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-04-01 | 2014 Merck KGaA
Collaboration agreements
Expected recognition period		10 years
Joint Research Committee Services | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-04-01 | 2014 Merck KGaA
Collaboration agreements
Expected recognition period		5 years