Income taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating Loss Carryforwards [Line Items]
Income tax expense	$ 0	$ 0
Increase in valuation allowance	9,200,000	7,400,000
Federal operating loss	92,600,000
State net operating loss	84,300,000
Net operating loss generated not subject to expiration	$ 75,600,000
Percentage of taxable income offset from net operating loss	80.00%
R&D tax credits	$ 200,000
Uncertain tax positions	37,000	$ 37,000
Federal
Operating Loss Carryforwards [Line Items]
Federal tax	$ 3,500,000