Refers to number of monthly payments an employee is entitled to receive under the defined benefit plan.

No definition available.

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- Definition

The percentage of average base compensation of the highest five consecutive years for normal retirement under defined benefit plan.

+ References

No definition available.

+ Details

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- Definition

Percentage employer matches of the employee's first 1% contribution matched.

+ References

No definition available.

+ Details

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- Definition

Percentage employer matches of the employee's next 5% contribution matched.

+ References

No definition available.

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- Definition

The percentage of participant's annual base salary received by beneficiary for years two through five following date of death.

+ References

No definition available.

+ Details

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- Definition

The percentage of participant's annual base salary received by beneficiary for one year from date of death.

+ References

No definition available.

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- Definition

The number of shares of the company's common stock owned by the plan.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

+ References

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of cost (credit) included in accumulated other comprehensive (income) loss expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

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- Definition

Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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- Definition

Amount of net periodic benefit cost (credit) for defined benefit plan.

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- Definition

Amount of cost for defined contribution plan.

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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

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- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Note 13 - Retirement Fund and Profit Sharing Plan (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Supplemental Employee Retirement Plan [Member]
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	$ 1,507	$ 1,839
Defined Benefit Plan, Accumulated Benefit Obligation	18,500	16,500
Investments, Fair Value Disclosure, Total	14,700	13,000
Defined Benefit Plan, Expected Amortization, Next Fiscal Year, Total	300
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	400
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	$ 1,100	1,300
Bel Fuse Inc. Employees' Savings Plan [Member] \| Common Class A [Member]
Shares Held in Plan \| shares	166,004
Bel Fuse Inc. Employees' Savings Plan [Member] \| Common Class B [Member]
Shares Held in Plan \| shares	108,868
Retirement Fund Covering Hong Kong-based Employees [Member]
Defined Contribution Plan, Cost	$ 300	$ 300
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 \| shares	3,323
Retirement Fund Covering Hong Kong-based Employees [Member] \| Common Class B [Member]
Shares Held in Plan \| shares	17,342