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Income taxes - Reconciliation of the Company's actual tax rate to the U.S. Federal statutory rate (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income tax rates
- Statutory U.S. federal rate	21.00%	21.00%	21.00%
- State income taxes, net of federal benefit	4.00%	4.00%	4.00%
- Excess tax benefits related to stock compensation	0.00%	(1.00%)	(1.00%)
- 162m limitation	1.00%	1.00%	1.00%
- Change in valuation allowance	0.00%	0.00%	(13.00%)
- Other true-up	(2.00%)	0.00%	(1.00%)
Total	24.00%	25.00%	11.00%
Federal
Income tax rates
Operating loss carryforwards	$ 0	$ 0
State
Income tax rates
Operating loss carryforwards	$ 1,400,000

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- Definition

Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to nondeductible expense for internal revenue code act limitation.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other true up.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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