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Note 9 - Income Taxes (Details Textual) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Unrecognized Tax Benefits, Ending Balance |  | $ 29,061 | $ 28,951 | $ 30,430
Liability for Uncertainty in Income Taxes, Current |  | 2,200 | 1,400 |
Liability for Uncertainty in Income Taxes, Noncurrent |  | 26,901 | 27,553 |
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations |  | 1,400 |  |
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total |  | 700 | 1,300 |
Income Tax Expense (Benefit) on Reversal of Interest and Penalties |  | 700 | 300 |
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total |  | 4,900 | 3,800 |
Income (Loss) from Continuing Operations before Income Taxes, Domestic |  | 17,100 | 300 |
Income (Loss) from Continuing Operations before Income Taxes, Foreign |  | $ 9,800 | $ 23,300 |
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent |  | 21.00% | 21.00% |
Deferred Tax Assets, Gross, Total |  | $ 23,335 | $ 18,949 |
Deferred Tax Assets, Valuation Allowance, Total |  | 8,216 | 9,200 |
Deferred Tax Assets, Operating Loss Carryforwards, Total |  | 8,042 | 8,370 |
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount |  | 200 |  |
Tax Cuts and Jobs Act, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense |  |  |  | $ 18,100
Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit) |  |  | (2,600) |
Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Income Tax Expense |  |  | 15,500 |
Other Current Liabilities [Member] |  |  |  |
Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Liability, Total |  |  | $ 10,800 |
Foreign Tax Authority [Member] |  |  |  |
Operating Loss Carryforwards, Total |  | 29,600 |  |
Tax Credit Carryforward, Amount |  | 300 |  |
Deferred Tax Assets, Gross, Total |  | 7,100 |  |
Deferred Tax Assets, Valuation Allowance, Total |  | 7,100 |  |
Foreign Tax Authority [Member] | Capital Loss Carryforward [Member] |  |  |  |
Tax Credit Carryforward, Amount |  | 200 |  |
Federal and State and Local Authority [Member] |  |  |  |
Operating Loss Carryforwards, Total |  | 1,500 |  |
Deferred Tax Assets, Valuation Allowance, Total |  | $ 1,100 |  |
Bel Fuse Limited [Member] |  |  |  |
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent |  | 12.00% |  |
Array [Member] | Federal and State and Local Authority [Member] |  |  |  |
Operating Loss Carryforwards, Total |  | $ 800 |  |
Tax Credit Carryforward, Amount |  | 2,100 |  |
Deferred Tax Assets, Operating Loss Carryforwards, Total |  | 200 |  |
Tax Year 2008 [Member] |  |  |  |
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations |  | 1,000 |  |
Tax Year 2015 [Member] |  |  |  |
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations |  | 100 |  |
Tax Year 2017 [Member] |  |  |  |
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations |  | $ 300 |  |
Forecast [Member] |  |  |  |
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations | $ 2,200 |  |  |
Forecast [Member] | Tax Year 2009 [Member] |  |  |  |
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations | 900 |  |  |
Forecast [Member] | Tax Year 2016 [Member] |  |  |  |
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations | $ 1,300 |  |  |

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