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Note 12 - Retirement, Savings and Deferred Compensation Plans (Details Textual) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($) shares	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) shares	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) shares
Bel Fuse Inc. Employees' Savings Plan [Member]
Defined Contribution Plan, Cost | $	$ 0.3	$ 0.3	$ 1.0	$ 0.9
Bel Fuse Inc. Employees' Savings Plan [Member] | Common Class A [Member]
Shares Held in Plan (in shares) | shares	313,559		313,559
Bel Fuse Inc. Employees' Savings Plan [Member] | Common Class B [Member]
Shares Held in Plan (in shares) | shares	93,789		93,789
Nonqualified Deferred Compensation Plan [Member]
Deferred Compensation Arrangement, Vesting Age	65		65
Deferred Compensation Plan Assets | $	$ 0.6		$ 0.6		$ 0.8
Nonqualified Deferred Compensation Plan [Member] | Maximum [Member]
Deferred Compensation Arrangement with Individual, Compensation Expense | $	0.1	0.1	0.1	0.1
Retirement Fund Covering Hong Kong-based Employees [Member]
Defined Contribution Plan, Cost | $	$ 0.4	$ 0.6	$ 1.3	$ 1.9
Retirement Fund Covering Hong Kong-based Employees [Member] | Common Class A [Member]
Shares Held in Plan (in shares) | shares	0		0		3,323
Retirement Fund Covering Hong Kong-based Employees [Member] | Common Class B [Member]
Shares Held in Plan (in shares) | shares	0		0		17,342

X

- Definition

The age of employees for contributions to become fully vested under deferred compensation arrangement.

+ References

No definition available.

+ Details

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X

- Definition

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

+ References

No definition available.

+ Details

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X

- Definition

The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 30
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363

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X

- Definition

Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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X

- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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