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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
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
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% | 0.00%
- Excess tax benefits related to stock compensation | (1.00%) | (1.00%) | (4.00%)
- 162m limitation | 1.00% | 1.00% |
- PPP Benefit | 0.00% | 0.00% | (2.00%)
- Valuation allowance | 0.00% | 13.00% | 12.00%
- Other true-up | 0.00% | (1.00%) |
Total | 25.00% | 11.00% | 3.00%
Domestic Tax Authority [Member] |  |  |
Income tax rates |  |  |
Operating loss carryforwards | $ 0 | $ 0 |
State |  |  |
Income tax rates |  |  |
Operating loss carryforwards | $ 1,800,000 |  |

X
- 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. + References No definition available. + Details
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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 benefit from Paycheck Protection program. + References No definition available. + Details
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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-12 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-12 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.Fact.4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1 + Details
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- Definition 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 applicable to state and local income tax expense (benefit), net of federal tax expense (benefit). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-12 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.Fact.4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1 + Details
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