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Stock compensation plan - Narrative (Details) - USD ($)	6 Months Ended
Stock compensation plan - Narrative (Details) - USD ($)	Jun. 30, 2024	Jun. 30, 2018	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized (in shares)		1,822,000	4,714,982
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cost not yet recognized	$ 300,000
Period for recognition	6 months
Options \| Minimum \| Share-based Payment Arrangement, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years
Options \| Minimum \| Share-based Payment Arrangement, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Options \| Minimum \| Share-based Payment Arrangement, Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Exchange Offer \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	7 years
Exchange Offer \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cost not yet recognized	$ 28,000,000.0
Period for recognition	2 years
Restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
2018 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Available for grant (in shares)	1,800,000
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized (in shares)		193,000
Available for grant (in shares)	14,200
Maximum employee payroll deduction percentage	15.00%
Common stock value, tax limit on employee stock purchase plan	$ 25,000
Purchase price of common stock (percent)	85.00%
Equity Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Available for grant (in shares)	1,600,000
Assumed Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Available for grant (in shares)	102,100