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