Document And Entity Information
Note To Financial Statement Details Textual
Significant Accounting Policies
Note 2 - Acquisition
Provision for income taxes
ecd_NonRule10b51ArrTrmntdFlag
Non-Rule 10b5-1 Arrangement Terminated [Flag]
Note 3 - Revenue
ecd_NonRule10b51ArrAdoptedFlag
Non-Rule 10b5-1 Arrangement Adopted [Flag]
Note 4 - Earnings Per Share
Trading Arrangements, by Individual [Table]
Note 5 - Fair Value Measurements
Assets, Fair Value, Cash and Cash Equivalents
The fair value amount of assets included in cash and cash equivalents.
Retirement Benefits [Text Block]
Material Terms of Trading Arrangement [Text Block]
Note 6 - Inventories
Note 7 - Property, Plant and Equipment
Financial Instrument [Axis]
Note 8 - Accrued Expenses
Note 9 - Derivative Instruments and Hedging Activities
Note 12 - Retirement, Savings and Deferred Compensation Plans
Note 13 - Accumulated Other Comprehensive Loss
Note 15 - Segments
Note 2 - Acquisition - Purchase Price Allocation (Details)
Note 2 - Acquisition - Pro Forma Information (Details)
Note 3 - Revenue - Disaggregation of Revenue by Product Group and Sales Channel (Details)
Note 3 - Revenue - Contract Assets and Contract Liabilities (Details)
Retirement Plan Name [Domain]
Litigation Case [Domain]
Note 4 - Earnings Per Share - Earnings Per Share (Details)
Note 5 - Fair Value Measurements - Fair Value Assets by Investment Category (Details)
us-gaap_IncreaseDecreaseInAccountsReceivable
Decrease in accounts receivable
Retirement Plan Type [Domain]
Note 5 - Fair Value Measurements - Fair Value of Derivative Financial Instruments (Details)
Retirement Plan Name [Axis]
Note 5 - Fair Value Measurements - Fair Value of Earnout Liabilities (Details)
Certificates of Deposit [Member]
Note 6 - Inventories - Components of Inventories (Details)
Retirement Plan Type [Axis]
Note 7 - Property, Plant and Equipment - Property, Plant and Equipment (Details)
Note 8 - Accrued Expenses - Accrued Expenses (Details)
Note 8 - Accrued Expenses - Activity and Liability Balances Related to Restructuring Costs (Details)
us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses
Net amortization
Note 9 - Derivative Instruments and Hedging Activities - Derivative Financial Instruments Effects on Accumulated Other Comprehensive Loss (Details)
Note 9 - Derivative Instruments and Hedging Activities - (Losses) Gains Recognized on Derivatives Instruments Not Designated as Hedging (Details)
Basis of Presentation and Significant Accounting Policies [Text Block]
Note 12 - Retirement, Savings and Deferred Compensation Plans - Components of SERP Expense (Details)
Business Combination, Contingent Consideration [Table Text Block]
Note 12 - Retirement, Savings, and Deferred Compensation Plans - Recognized in Accumulated Other Comprehensive Loss (Details)
Note 13 - Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Loss (Details)
Note 13 - Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Loss (Details) (Parentheticals)
Note 13 - Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss by Component (Details)
Note 15 - Segments - Segmented Earnings Breakdown (Details)
Note 15 - Segments - Segment Information (Details)
Notes To Financial Statements
Notes To Financial Statements [Abstract]
us-gaap_ForeignCurrencyTransactionGainLossUnrealized
Unrealized losses (gains) on foreign currency revaluation
Income Tax Jurisdiction [Domain]
Less dividends declared
Cash dividends declared on common stock
Interest cost
Land [Member]
us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable
(Decrease) increase in income taxes payable
Financial Instruments [Domain]
Dividends declared (in dollars per share)
Litigation Case [Axis]
us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
Net periodic benefit cost
us-gaap_IncreaseDecreaseInInventories
Increase in inventories
Net loss
us-gaap_SharesOutstanding
Balance (in shares)
Balance (in shares)
Service cost
Prior service cost
Segment Reporting [Text Block]
Employee Severance [Member]
Type of Restructuring [Domain]
Segment Reporting [Table Text Block]
Preferred stock, no par value, 1,000,000 shares authorized; none issued
Adjustments to reconcile net earnings to net cash provided by operating activities:
Segment Reporting, Reconciliation of Profit (Loss) by Segment to Consolidated [Table Text Block]
us-gaap_Liabilities
Total liabilities
Defined Benefit Plan [Table]
Restructuring and Related Costs [Table Text Block]
us-gaap_LiabilitiesAndStockholdersEquity
Total liabilities, redeemable noncontrolling interest and shareholders' equity
Consolidation Items [Axis]
Segment Reporting [Table]
Condensed Balance Sheet Statement [Table]
Selling, general and administrative expenses
Stock-based compensation
Consolidation Items [Domain]
Unrealized losses (gain) on interest rate swap cash flow hedge, tax
Unrealized losses on interest rate swap cash flow hedge, net of taxes of $0 in all periods presented
Net gains (losses) recognized in AOCL
Unrealized gains on interest rate swap cash flow hedge, net of taxes of $0 at March 31, 2026 and $0 at December 31, 2025
Changes in operating assets and liabilities:
North America [Member]
us-gaap_IncreaseDecreaseInAccountsPayable
Increase (decrease) in accounts payable
Net gains (losses) reclassified from AOCL to the consolidated statement of operations
Preferred stock, shares issued (in shares)
Europe [Member]
Asia [Member]
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Preferred stock, shares authorized (in shares)
Portion at Fair Value Measurement [Member]
Reported Value Measurement [Member]
Fair Value, by Balance Sheet Grouping [Table]
us-gaap_IncreaseDecreaseInAccruedLiabilities
Decrease in accrued expenses
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect
Net increase (decrease) in cash and cash equivalents
Effect of exchange rate changes on cash and cash equivalents
Estimate of Fair Value Measurement [Member]
Earnout payment liability - 2025
Earnout payment liability - 2026
New Accounting Pronouncements, Policy [Policy Text Block]
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations
Cash and cash equivalents - beginning of period
Cash and cash equivalents - end of period
Statement [Table]
Credit Facility [Axis]
Credit Facility [Domain]
Revolving Credit Facility [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]
Sales Channel, Directly to Consumer [Member]
ROU assets obtained in exchange for lease obligations
us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Line of Credit Facility, Maximum Borrowing Capacity
Line of Credit Facility, Lender [Domain]
belfa_ContractWithCustomerLiabilityAdvancePaymentsReceived
Contract With Customer, Liability, Advance Payments Received
The amount of advance payments received from customers for goods or services to be provided at a later date.
Lender Name [Axis]
us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Line of Credit Facility, Remaining Borrowing Capacity
us-gaap_LineOfCredit
Long-Term Line of Credit
belfa_PaymentForCustomsDutiesAndImposedFinesAndPenalties
Payment for Customs Duties and Imposed Fines and Penalties
The amount of cash outflow for payment for customs duties and imposed fines and penalties.
Asset Class [Axis]
EOS Claim From Principal Commissioner of Customs [Member]
Related to EOS claim from principal commissioner of customs.
belfa_CustomsDutiesAndImposedFines
Customs Duties and Imposed Fines
The value of customs duties and imposed fines.
Measurement Frequency [Axis]
Commitments and Contingencies Disclosure [Text Block]
Statement [Line Items]
Fair Value Hierarchy and NAV [Axis]
Common stock, shares outstanding (in shares)
Common stock, shares authorized (in shares)
Common Class B [Member]
Schedule of Accrued Liabilities [Table Text Block]
Common Stock
Schedule of Inventory, Current [Table Text Block]
Business Combination, Recognized Asset Acquired and Liability Assumed [Table Text Block]
Segment gross profit %
Represents percentage of gross profit.
Accounts payable
us-gaap_PolicyTextBlockAbstract
Accounting Policies
us-gaap_ProductWarrantyExpense
Product Warranty Expense
us-gaap_DisclosureTextBlockAbstract
Notes to Financial Statements
us-gaap_TableTextBlock
Notes Tables
Comprehensive Income (Loss) Note [Text Block]
Borrowings under revolving line of credit
us-gaap_ComprehensiveIncomeNetOfTax
Comprehensive income attributable to Bel shareholders
Capital Expenditures
Accrued expenses
Accrued Liabilities, Current
Salaries, bonuses and related benefits
Sales commissions
Warranty accrual
Operating lease liabilities, long-term
Other
Operating lease liabilities, current
Less: Net earnings attributable to noncontrolling interest
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]
us-gaap_LongTermDebtPercentageBearingFixedInterestRate
Long-Term Debt, Percentage Bearing Fixed Interest, Percentage Rate
us-gaap_LongTermDebtPercentageBearingVariableInterestRate
Long-Term Debt, Percentage Bearing Variable Interest, Percentage Rate
Business Combination, Contingent Consideration, Type [Domain]
Long-term debt
Business Combination, Contingent Consideration, Type [Axis]
Income Tax Jurisdiction, Domestic Federal [Member]
Proceeds from disposal/sale of property, plant and equipment
Income Tax Jurisdiction, Domestic State and Local [Member]
Other comprehensive income (loss):
Statement of Stockholders' Equity [Abstract]
Statement of Comprehensive Income [Abstract]
Statement of Cash Flows [Abstract]
us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
Other comprehensive income (loss)
Shareholders' Equity:
us-gaap_LossContingencyEstimateOfPossibleLoss
Loss Contingency, Estimate of Possible Loss
Equity Components [Axis]
Equity Component [Domain]
Fair Value, Inputs, Level 2 [Member]
us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet
Total consideration paid
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Fair Value, Inputs, Level 3 [Member]
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
Fair Value, Inputs, Level 1 [Member]
AOCI Attributable to Parent [Member]
Additional Paid-in Capital [Member]
Retained Earnings [Member]
Cost of sales
Inventory impairment
Property, plant and equipment, net
Property, plant and equipment, net
Property, plant and equipment, gross
Minimum pension obligation and unfunded pension liability
us-gaap_DeferredIncomeTaxAssetsNet
Deferred income taxes
Machinery and Equipment [Member]
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]
Schedule of Net Benefit Costs [Table Text Block]
Stock-based compensation expense
us-gaap_DeferredIncomeTaxLiabilitiesNet
Deferred income taxes
The 2021 Swaps One [Member]
The first of the 2021 interest rate swaps.
Accounts Payable and Accrued Liabilities Disclosure [Text Block]
The 2021 Swaps Two [Member]
The second of the 2021 interest rate swaps.
Foreign currency translation adjustment, net of taxes of ($312) at March 31, 2026 and ($312) at December 31, 2025
us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax
Fair Value Disclosures [Text Block]
Sales Channel, Through Intermediary [Member]
Supplementary information:
Current Liabilities:
us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill
Impairment of Intangible Assets, Indefinite-Lived (Excluding Goodwill)
us-gaap_LiabilitiesCurrent
Total current liabilities
Derivatives Not Designated as Hedging Instruments [Table Text Block]
us-gaap_DebtInstrumentVariableInterestRateTypeExtensibleEnumeration
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]
Accounts receivable, net of allowance of $825 and $671, respectively
Accounts receivable, net
us-gaap_LongTermDebtFairValue
Long-Term Debt, Fair Value
Derivative Instruments and Hedging Activities Disclosures [Table]
Supplemental Employee Retirement Plan [Member]
Other Commitments [Table]
us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
Accumulated depreciation
Accumulated other comprehensive loss
Accumulated other comprehensive loss
us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
Acquisition of business, net of cash acquired
us-gaap_LongtermDebtPercentageBearingVariableInterestAmount
Long-Term Debt, Percentage Bearing Variable Interest, Amount
us-gaap_PaymentsToAcquireNotesReceivable
Investment in related party notes receivable
Earnings before provision for income taxes
Earnings before provision for income taxes
us-gaap_LongtermDebtPercentageBearingFixedInterestAmount
Long-Term Debt, Percentage Bearing Fixed Interest, Amount
Additional paid-in capital
Debt Disclosure [Text Block]
Issuance of restricted common stock
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
us-gaap_PaymentsToAcquirePropertyPlantAndEquipment
Purchase of property, plant and equipment
Redemption value adjustment attributable to noncontrolling interest
us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders
Redemption value adjustment attributable to noncontrolling interest
Undistributed earnings
us-gaap_DebtInstrumentCarryingAmount
Long-Term Debt, Gross
Current Assets:
Money Market Funds [Member]
us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardForfeitures
Forfeiture of restricted common stock
us-gaap_AssetsCurrent
Total current assets
Segment gross profit
Gross profit
belfa_BusinessCombinationRecognizedAssetAcquiredAssetIncludingGoodwill
Net assets acquired
Amount of asset including goodwill acquired in business combination and recognized at acquisition date.
us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent
Amount reclassified from accumulated other comprehensive loss
us-gaap_DebtInstrumentInterestRateStatedPercentage
Debt Instrument, Interest Rate, Stated Percentage
us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardForfeited
Forfeiture of restricted common stock (in shares)
Other comprehensive (loss) income before reclassifications
us-gaap_Depreciation
Depreciation
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block]
us-gaap_DebtInstrumentInterestRateEffectivePercentage
Debt Instrument, Interest Rate, Effective Percentage
Issuance of restricted common stock (in shares)
Class of Stock [Domain]
us-gaap_RedeemableNoncontrollingInterestEquityFairValue
Redeemable Noncontrolling Interest, Equity, Fair Value
Schedule of Long-Term Debt Instruments [Table]
us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount
Redeemable noncontrolling interest
Cash flows from operating activities:
Cash flows from investing activities:
Raw materials
us-gaap_NetCashProvidedByUsedInOperatingActivities
Net cash provided by operating activities
Work in progress
Cash flows from financing activities:
us-gaap_NetCashProvidedByUsedInInvestingActivities
Net cash used in investing activities
Finished goods
us-gaap_NetCashProvidedByUsedInFinancingActivities
Net cash provided by (used in) financing activities
Liability for uncertain tax positions
Restructuring Type [Axis]
EOS Power Panama Inc. [Member]
Represents EOS Power Panama Inc.
Assets, fair value
Assets, Fair Value Disclosure, Total
Operating Segments [Member]
Accounting Policies [Abstract]
us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense
Deferred Compensation Arrangement with Individual, Compensation Expense
Segments [Domain]
Unrealized holding gains on marketable securities, net of taxes of ($7) at March 31, 2026 and ($7) at December 31, 2025
us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax
Unfunded SERP liability, net of taxes of $1,000 at March 31, 2026 and $1,003 at December 31, 2025
us-gaap_DeferredCompensationPlanAssets
Deferred Compensation Plan Assets
Accounts receivable, allowance for doubtful accounts
Unrealized gains of interest rate swap cash flow hedge, tax
Amount of tax on accumulated gain (loss) on derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.
Segments [Axis]
Measurement Input Type [Axis]
Income Statement [Abstract]
us-gaap_UnrecognizedTaxBenefits
Unrecognized Tax Benefits
belfa_ContractWithCustomerLiabilityRevenueRecognizedDuringPeriod
Contract with Customer, Liability, Revenue Recognized During Period
Amount of revenue recognized during period from contract with customer.
us-gaap_NumberOfReportableSegments
Number of Reportable Segments
Measurement Input, Expected Term [Member]
Common stock, treasury shares (in shares)
Measurement Input, Discount Rate [Member]
us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations
Net earnings
us-gaap_NetIncomeLoss
Net earnings attributable to Bel Fuse shareholders
Measurement Input, Price Volatility [Member]
Net earnings attributable to Bel shareholders
Net earnings available to common shareholders
belfa_BusinessAcquisitionProFormaProfitLoss
Net earnings
The pro forma net Income or Loss including noncontrolling interests for the period as if the business combination or combinations had been completed at the beginning of a period.
Full Achievement of Earnout [Member]
Relating to the full achievement of Earnout.
Earnout Payment [Member]
Relating to earnout payment.
Less than 90% of Earnout [Member]
Relating to less than 90% of earnout.
Amortization of deferred financing costs
Above 90% and Less Than 100% Achievement of Earnout [Member]
Relating to above 90% and less than 100% achievement of earnout.
Common Class A [Member]
Measurement Input Type [Domain]
belfa_BusinessAcquisitionProFormaNetIncomeLossAttributableToNoncontrollingInterests
Less: Net earnings attributable to non-controlling interest
The pro forma net Income or Loss attributable to noncontrolling interests for the period as if the business combination or combinations had been completed at the beginning of a period.
us-gaap_OtherNoncashIncomeExpense
Other, net
Money Market Funds, Rabbi Trust [Member]
Relating to money market funds attributable to a rabbi trust.
us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput
Business Combination, Contingent Consideration, Liability, Measurement Input
Accumulated Other Comprehensive Income (Loss) [Table]
us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued
us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense
Income Tax Disclosure [Text Block]
Business Combination, Contingent Consideration, Liability
us-gaap_BusinessCombinationContingentConsiderationLiability
Business Combination, Contingent Consideration, Liability
Accounting Standards Update and Change in Accounting Principle [Table]
belfa_PolicyTable
us-gaap_BusinessCombinationPriceOfAcquisitionExpected
Business Combination, Price of Acquisition, Expected
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax
Measurement Basis [Axis]
Fair Value Hierarchy and NAV [Domain]
Measurement Frequency [Domain]
Nonqualified Deferred Compensation Plan [Member]
Represents Nonqualified Deferred Compensation Plan.
belfa_DeferredCompensationArrangementVestingAge
Deferred Compensation Arrangement, Vesting Age
The age of employees for contributions to become fully vested under deferred compensation arrangement.
us-gaap_OpenTaxYear
Open Tax Year
Interest income
Interest income
us-gaap_RepaymentsOfLinesOfCredit
Repayments under revolving line of credit
Statement of Financial Position [Abstract]
Income taxes, net of refunds received
Long-term Liabilities:
Fair Value, Nonrecurring [Member]
Other assets
Document Type
Document Information [Line Items]
Document Quarterly Report
us-gaap_DefinedContributionPlanCostRecognized
Defined Contribution Plan, Cost
us-gaap_IncreaseDecreaseInOtherNoncurrentAssets
Decrease in other assets
Restructuring charges
Document Information [Table]
us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)
us-gaap_IncreaseDecreaseInOtherCurrentAssets
Increase in other current assets
us-gaap_BusinessAcquisitionsProFormaRevenue
Revenue, net
Entity Interactive Data Current
Document Transition Report
us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
Class B common share - diluted (in shares)
Net earnings per common share:
us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted
Earnings per Class A common share - basic and diluted (in dollars per share)
us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic
Earnings per Class A common share - basic (in dollars per share)
us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss
Net earnings attributable to Bel Fuse shareholders
us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Class A common share - basic and diluted (in shares)
Derivative Instrument [Axis]
Class A common share - basic and diluted (in dollars per share)
Net earnings per share, basic (in dollars per share)
Earnings Per Share, Basic, by Common Class, Including Two-Class Method [Table]
Effective Income Tax Rate Reconciliation [Table]
EMEA [Member]
Income Tax Jurisdiction [Axis]
Intangible assets, net
Document Fiscal Period Focus
Document Fiscal Year Focus
Amendment Flag
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Accrued restructuring costs
Goodwill, net
Goodwill
Decrease in other liabilities
Document Period End Date
Property, Plant, and Equipment [Text Block]
Long-Lived Asset, Class [Domain]
us-gaap_DerivativeBasisSpreadOnVariableRate
Derivative, Basis Spread on Variable Rate
Legal Entity [Axis]
Construction in Progress [Member]
Business Combination [Domain]
Entity File Number
us-gaap_RevenueRemainingPerformanceObligation
Revenue, Remaining Performance Obligation, Amount
us-gaap_DerivativeFixedInterestRate
Derivative, Fixed Interest Rate
Entity Tax Identification Number
Business Combination [Axis]
Investments Held in Rabbi Trust [Member]
Information pertaining to investments held in a rabbi trust which are intended to fund the Company's Supplemental Executive Retirement Plan ("SERP").
Bel Fuse Inc. Employees' Savings Plan [Member]
Information pertaining to the Bel Fuse Inc. Employees' Savings Plan.
Disaggregation of Revenue [Table Text Block]
Disaggregation of Revenue [Table]
Entity [Domain]
Entity Central Index Key
us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Business Acquisition, Percentage of Voting Interests Acquired
Credit and Security Agreement with KeyBank [Member]
Information pertaining to the Credit and Security Agreement with KeyBank National Association (as amended, the "CSA").
Entity Registrant Name
belfa_RestructuringCashPaymentsAndOtherSettlements
Cash payment and other settlements
The amount of cash payments made as the result of exit or disposal activities and any other settlements which is not reported separately during the period.
Foreign currency translation adjustment, net of taxes
us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
Currency translation adjustment, net of taxes of $0, and $0, respectively
Entity Current Reporting Status
Business Combination [Table]
belfa_SharesHeldInPlan
Shares Held in Plan (in shares)
The number of shares of the company's common stock owned by the plan.
Entity Incorporation, State or Country Code
Business Combination, Pro Forma Information [Table Text Block]
Current Fiscal Year End Date
us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables
Accounts receivable
us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory
Inventories
Contract with Customer, Sales Channel [Domain]
Research and development costs
Entity Filer Category
Arezzo Revenue Agency [Member]
Information pertaining to Arezzo Revenue Agency.
Entity Shell Company
us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities
Working Capital Liabilities
Contract with Customer, Sales Channel [Axis]
Entity Emerging Growth Company
us-gaap_DerivativeNotionalAmount
Derivative, Notional Amount
belfa_NumberOfIndustryInWhichEntityOperates
Number of Industry in which Entity Operates
Number of industry in which entity operates with its reportable operating segments.
Entity Small Business
Foreign currency translation adjustment, tax expense
Building and Building Improvements [Member]
us-gaap_OperatingIncomeLoss
Income from operations
Total derivative assets
Derivative Asset
Foreign currency translation adjustment, tax
belfa_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax
Represents the tax expense (benefit) arising from the accumulated appreciation or loss in value of foreign currency translation adjustment at the end of an accounting period.
us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet
Derivative Assets (Liabilities), at Fair Value, Net
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets
Total identifiable assets
us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment
Net Fixed Assets
us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
Derivative instruments gain (loss)
belfa_AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax
Change in unfunded SERP liability, tax
Represents the tax portion in relation to net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other post-retirement plan(s) because they have yet to be recognized as components of net periodic benefit cost.
Not designated as hedging instruments
Unrealized holding gains on available-for-sale securities, tax
Represents the tax expense (benefit) of arising from the accumulated appreciation or loss in value of total available-for-sale securities at the end of an accounting period.
us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High
Derivative Instruments and Hedging Activities Disclosure [Text Block]
belfa_IndemnificationPeriod
Indemnification Period (Year)
The period of indemnification.
us-gaap_InterestExpenseDebt
Interest Expense, Debt
us-gaap_BusinessCombinationConsiderationTransferred1
Business Combination, Consideration Transferred
Entity Address, State or Province
Inventory, Current [Table]
Entity Address, City or Town
Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component [Table Text Block]
Tabular disclosure of changes in components of accumulated other comprehensive income (loss).
Interest expense
Interest expense
Retained earnings
Issuance of shares upon vesting of Performance Stock Units
Entity Address, Address Line One
Unbilled receivables
Contract assets - current (unbilled receivables)
City Area Code
Local Phone Number
Entity Address, Postal Zip Code
Revenue from Contract with Customer [Text Block]
us-gaap_IncreaseDecreaseInRestructuringReserve
Decrease in accrued restructuring costs
Title of 12(b) Security
Security Exchange Name
Change in unfunded SERP liability, tax
Trading Symbol
Change in unfunded SERP liability, net of taxes
us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax
Change in unfunded SERP liability, net of taxes of $3 and $8, respectively
Class of Stock [Axis]
us-gaap_AvailableForSaleSecuritiesDebtSecurities
Debt Securities, Available-for-Sale
Variable Rate [Domain]
Entity Common Stock, Shares Outstanding
Earnings Per Share [Text Block]
Preferred stock, no par value (in dollars per share)
Other current assets
Unrealized gain on marketable securities arising during the period, tax
Unrealized holding losses on marketable securities, net of taxes of $0 in all periods presented
Weighted-average number of shares outstanding:
Net earnings
us-gaap_ProfitLoss
Net earnings available to common shareholders
Deferred tax benefit
dataMate [Member]
Represents information pertaining to dataMate.
Scenario [Axis]
Scenario [Domain]
Forecast [Member]
Derivative Instruments, Gain (Loss) [Table Text Block]
Property, Plant, and Equipment [Table]
Common stock, par value (in dollars per share)
Derivative Contract [Domain]
Other (expense) income, net
Other income, net
Long-Lived Asset, Class [Axis]
Total Assets
Total assets
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]
Cash and cash equivalents
Geographical [Domain]
Other Restructuring [Member]
Geographical [Axis]
Cash [Member]
Designated as cash flow hedges
Designated as a cash flow hedge
Class B common share - diluted (in dollars per share)
Net earnings per share, diluted (in dollars per share)
us-gaap_ContractWithCustomerLiability
Contract with Customer, Liability
Redemption value adjustment attributable to noncontrolling interest
The value of redemption value adjustment attributable to noncontrolling interest.
us-gaap_ContractWithCustomerLiabilityCurrent
Contract liabilities - current (deferred revenue)
us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther
Other current assets
Depreciation and amortization
Depreciation and Amortization Expense
Common Stock Outstanding [Member]
Represents common stock outstanding.
Asset Class [Domain]
Aerospace, Defense, and Rugged Solutions Segment [Member]
Represents information pertaining to Aerospace, Defense, and Rugged Solutions segments.
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Industrial Technology and Data Solutions Segment [Member]
Represents information pertaining to the Industrial Technology and Data Solutions segment.
Interest payments
Interest Rate Swap [Member]
Inventory Disclosure [Text Block]
Comprehensive income attributable to noncontrolling interest
us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
Comprehensive income
us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
Balance
Balance
Enercon Technologies, Ltd [Member]
In reference to Enercon Technologies, Ltd.
Inventories
Inventories
Business Combination [Text Block]
Noncontrolling Interest [Member]
us-gaap_IncreaseDecreaseInContractWithCustomerLiability
Increase (Decrease) in Contract with Customer, Liability
us-gaap_StockholdersEquity
Total shareholders' equity
Balance
Balance
us-gaap_IncreaseDecreaseInContractWithCustomerAsset
Decrease (increase) unbilled receivables
us-gaap_PaymentsOfDividends
Dividends paid to common shareholders
us-gaap_PaymentForContingentConsiderationLiabilityInvestingActivities
Payment for Contingent Consideration Liability, Investing Activities
Foreign Exchange Forward [Member]
Right-of-use assets
Other current liabilities
Other long-term liabilities
us-gaap_OtherLiabilitiesNoncurrent
Assets, Fair Value, Other Current Assets
The fair value amount for assets included in other current assets.
belfa_EarnoutLiabilityAdjustment
Earnout liability adjustment
The amount of adjusted earnout liability.
ecd_Rule10b51ArrTrmntdFlag
Rule 10b5-1 Arrangement Terminated [Flag]
Property, Plant, and Equipment [Table Text Block]
Net sales
ecd_Rule10b51ArrAdoptedFlag
Rule 10b5-1 Arrangement Adopted [Flag]
Commitments and contingencies (see Note 15)