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Note 15 - Retirement Fund and Profit Sharing Plan (Details Textual) $ in Thousands | 12 Months Ended | 24 Months Ended
--- | --- | ---
Dec. 31, 2024 USD ($) shares | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2024 USD ($) shares
Supplemental Employee Retirement Plan [Member] |  |  |  |
Deferred Compensation Arrangement with Individual, Compensation Expense |  |  |  | $ 100
Defined Benefit Plan, Percentage of Average Base Compensation Five Consecutive Years, Normal Retirement | 40.00% |  |  |
Defined Benefit Plan, Number of Monthly Payments | 120 |  |  |
Percentage of Participant's Annual Base Salary Received by Beneficiary, One Year From Date of Death | 100.00% |  |  |
Percentage of Participant's Annual Base Salary Received by Beneficiary, Following Four Years From Date of Death | 50.00% |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) | $ 1,377 | $ 1,326 | $ 1,451 |
Defined Benefit Plan, Accumulated Benefit Obligation | 17,200 | 18,100 |  | 17,200
Investments, Fair Value Disclosure | 17,000 | 15,400 |  | 17,000
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year | 900 |  |  | 900
Defined Benefit Plan, Plan Assets, Amount, Ending Balance | $ 0 |  |  | $ 0
Bel Fuse Inc. Employees' Savings Plan [Member] |  |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent Of Match, First 1% Employee Contribution | 100.00% |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match, Next 5% Employee Contribution | 50.00% |  |  |
Defined Contribution Plan, Cost | $ 1,400 | 1,300 | 1,300 |
Bel Fuse Inc. Employees' Savings Plan [Member] | Common Class A [Member] |  |  |  |
Shares Held in Plan (in shares) | shares | 256,585 |  |  | 256,585
Bel Fuse Inc. Employees' Savings Plan [Member] | Common Class B [Member] |  |  |  |
Shares Held in Plan (in shares) | shares | 52,924 |  |  | 52,924
Nonqualified Deferred Compensation Plan [Member] |  |  |  |
Deferred Compensation Arrangement, Vesting Age | 65 |  |  | 65
Deferred Compensation Plan Assets | $ 1,300 | 1,000 |  | $ 1,300
Nonqualified Deferred Compensation Plan [Member] | Maximum [Member] |  |  |  |
Deferred Compensation Arrangement with Individual, Compensation Expense | 200 | 200 | 100 |
Retirement Fund Covering Hong Kong-based Employees [Member] |  |  |  |
Defined Contribution Plan, Cost | $ 300 | $ 1,500 | $ 1,800 |
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent | 5.00% |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 7.00% |  |  |
Retirement Fund Covering Hong Kong-based Employees [Member] | Minimum [Member] |  |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 5.00% |  |  |

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