Income taxes - Reconciliation of benefit for income taxes (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income taxes
Provision for (benefit from) income taxes at statutory rate	23.50%	19.00%	19.00%
(Decreases) increases resulting from:
Federal tax credits	0.30%	0.30%	0.60%
Change in valuation allowance	(14.80%)	(16.80%)	(27.00%)
Net losses surrendered for research credit	(11.10%)	(6.50%)	(5.90%)
Impact of statutory rate change	2.70%	11.30%	12.10%
Impact of foreign exchange rates	(0.10%)	(9.90%)
Other	(1.30%)	3.90%	3.60%
Effective income tax rate	(0.80%)	1.30%	2.40%