Income taxes - Narrative (Details)	12 Months Ended
	Dec. 31, 2024 USD ($) jurisdiction	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Income Tax Examination [Line Items]
Income tax benefit	$ 418,000	$ 0	$ 0
Valuation allowance	262,845,000	239,468,000
Increase (decrease) in valuation allowance	23,400,000
Unrecognized tax benefits	0	0
Accrued interest or penalties related to uncertain tax position	$ 0	$ 0
Income taxes, number of state jurisdictions | jurisdiction	10
Open tax year	2020 2021 2022 2023 2024
Federal
Income Tax Examination [Line Items]
Net operating loss carry forwards	$ 462,200,000
Net operating loss carryforwards subject to expiration	10,600,000
Net operating loss carryforwards not subject to expiration	451,600,000
Federal | Research and development
Income Tax Examination [Line Items]
Tax credit carryforwards	28,200,000
State
Income Tax Examination [Line Items]
Net operating loss carry forwards	394,900,000
State | Research and development
Income Tax Examination [Line Items]
Tax credit carryforwards	$ 7,200,000