Summary of significant accounting policies and basis of presentation - Collaborative Arrangement Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement revenue	$ 32,358	$ 26,921	$ 115,594
Regeneron Collaboration Agreement | Collaboration Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement revenue	19,577	7,496	7,398
Bristol-Myers Squibb | ABECMA Commercial Activities
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement revenue	$ 12,781	$ 19,425	$ 108,196