Income taxes - Net operating loss carryforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income taxes
Valuation Allowance	$ 105,854	$ 82,612
Change in the valuation allowance	$ (23,300)
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income tax computed at federal statutory tax rate	21.00%	21.00%	21.00%
State taxes, net of federal benefit	9.30%	5.40%	5.20%
General business credits	8.30%	(0.40%)	(3.50%)
Provision to return	0.10%	0.90%	3.20%
Non-deductible expenses	(1.10%)	0.50%	(4.60%)
Other	(3.40%)	(0.40%)
Change in valuation allowance	(35.00%)	(26.00%)	(21.30%)
Total	(0.80%)	1.00%
Federal
Income taxes
Net operating loss carryforwards	$ 20,000
State
Income taxes
Net operating loss carryforwards	800
Investment tax credit	400
Research and development tax credits carryforwards | Federal
Income taxes
Tax credits carryforwards	23,600
Research and development tax credits carryforwards | State
Income taxes
Tax credits carryforwards	$ 13,730