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Note 14 - Retirement Fund and Profit Sharing Plan (Details Textual) $ in Thousands | 12 Months Ended
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Dec. 31, 2022 USD ($) shares | Dec. 31, 2021 USD ($) 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), Total | $ 1,451 | $ 1,726
Defined Benefit Plan, Accumulated Benefit Obligation | 17,000 | 21,800
Investments, Fair Value Disclosure, Total | 14,000 | 16,400
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year | 800 |
Defined Benefit Plan, Plan Assets, Amount, Ending Balance | $ 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 | $ 1,300 | 1,200
Bel Fuse Inc. Employees' Savings Plan [Member] | Common Class A [Member] |  |
Shares Held in Plan (in shares) | shares | 311,417 |
Bel Fuse Inc. Employees' Savings Plan [Member] | Common Class B [Member] |  |
Shares Held in Plan (in shares) | shares | 92,809 |
Nonqualified Deferred Compensation Plan [Member] |  |
Deferred Compensation Arrangement, Vesting Age | 65 |
Deferred Compensation Plan Assets | $ 700 | 800
Nonqualified Deferred Compensation Plan [Member] | Maximum [Member] |  |
Deferred Compensation Arrangement with Individual, Compensation Expense | 100 | 100
Retirement Fund Covering Hong Kong-based Employees [Member] |  |
Defined Contribution Plan, Cost | $ 1,800 | $ 2,700
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% |
Retirement Fund Covering Hong Kong-based Employees [Member] | Common Class A [Member] |  |
Shares Held in Plan (in shares) | shares | 0 | 3,323
Retirement Fund Covering Hong Kong-based Employees [Member] | Common Class B [Member] |  |
Shares Held in Plan (in shares) | shares |  | 17,342

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