Statement of Financial Position [Abstract] Cash and cash equivalents Marketable securities Accounts receivable, net of allowance for doubtful accounts of $182 at October 31, 2019 and $183 at April 30, 2019 Allowance for doubtful accounts (in Dollars) Costs and estimated earnings in excess of billings, net Inventories, net Inventory, Net Prepaid income taxes Prepaid expenses and other Current assets held for sale Total current assets Property, plant and equipment, at cost, net of accumulated depreciation and amortization Goodwill Cash surrender value of life insurance and cash held in trust Right-of-Use assets Operating lease ROU assets Other assets Non-current assets held for sale Total assets Identifiable Assets Accounts payable – trade Accrued liabilities Loss provision accrual Lease liability, current Operating lease liabilities (short-term) Less current obligations under leases Current liabilities held for sale Total current liabilities Deferred compensation Lease liability Operating lease liabilities (long-term) Long-term lease obligations Other liabilities Non-current liabilities held for sale Total liabilities Commitments and contingencies Preferred stock - $1.00 par value; authorized 600 shares, no shares issued Preferred stock, par value (in Dollars per share) Common stock - $1.00 par value; authorized 20,000 shares, 9,164 shares issued, 9,100 shares outstanding at October 31, 2019; 8,980 shares outstanding at April 30, 2019 Common stock, par value (in Dollars per share) Common stock shares issued Additional paid-in capital Accumulated deficit Common stock reacquired and held in treasury - at cost (64 shares at October 31, 2019 and 184 shares at April 30, 2019) Treasury stock, shares Accumulated other comprehensive income Total stockholders’ equity Balance Balance Total liabilities and stockholders’ equity Income Statement [Abstract] Revenues Revenues Revenue Cost of revenues Gross margin Selling and administrative expenses Research and development expense Operating loss Operating profit (loss) Investment income Interest expense Other income, net (Loss) Income before provision (benefit) for income taxes Provision (benefit) for income taxes Net (loss) income Net (loss) income Net income (loss) Basic and diluted (loss) earnings per share (in Dollars per share) Basic (in Shares) Basic Diluted (in Shares) Diluted Foreign currency translation adjustment Change in market value of marketable securities before reclassification, net of tax Reclassification adjustment for realized gains included in net income, net of tax Total unrealized gain (loss) on marketable securities, net of tax Total other comprehensive income (loss) Other comprehensive income, net of tax Comprehensive (loss) income Statement of Cash Flows [Abstract] Non-cash charges to earnings Net changes in operating assets and liabilities Net cash provided by (used in) operating activities Proceeds on redemption of marketable securities Purchase of marketable securities Purchase of fixed assets and other assets Net cash used in investing activities Net decrease in cash and cash equivalents before effect of exchange rate changes Effect of exchange rate changes on cash and cash equivalents Net decrease in cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Interest Income Taxes Income Taxes Statement of Stockholders' Equity [Abstract] Balance (in Shares) Balance (in Shares) Equity Components [Axis] Common Stock [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Treasury Stock [Member] AOCI Attributable to Parent [Member] Disclosure Text Block [Abstract] Earnings Per Share [Abstract] Schedule of Earnings Per Share, Basic and Diluted [Abstract] Contractors [Abstract] Costs and Estimated Earnings in Excess of Billings, Net [Abstract] Costs and estimated earnings in excess of billings Billings in excess of costs and estimated earnings Net asset Disclosure Text Block Supplement [Abstract] Inventory Disclosure [Abstract] Schedule of Inventory, Current [Abstract] Raw Materials and Component Parts Work in Progress Finished Goods Lessee, Operating Lease, Disclosure [Abstract] Total lease liabilities Present value of future lease payments Operating Lease, Liability Schedule of Future Minimum Rental Payments for Operating Leases [Abstract] Total future minimum lease payments Lessee, Operating Lease, Liability, Maturity [Abstract] Total lease payments Segment Reporting [Abstract] Reconciliation of Revenue from Segments to Consolidated [Abstract] Segments [Axis] Frequency Electronics Inc New York [Member] Frequency Electronics Inc Zyfer [Member] Inter Segment [Member] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract] Corporate Segment [Member] Schedule of Reconciliation of Assets from Segment to Consolidated [Abstract] Disaggregation of Revenue [Abstract] Product and Service [Axis] POC Revenue [Member] POT Revenue [Member] Revenue from External Customers by Products and Services [Abstract] Satellite Revenue [Member] Government Non-Space Revenue [Member] Other Commercial & Industrial Revenue [Member] Investment Holdings [Abstract] Investments, Debt and Equity Securities [Abstract] Schedule of Available-for-sale Securities Reconciliation [Abstract] Financial Instrument [Axis] Fixed Income Securities [Member] Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] Investments Classified by Contractual Maturity Date [Abstract] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Debt Disclosure [Abstract] Income Tax Disclosure [Abstract] Amendment Flag Current Fiscal Year End Date Document Fiscal Period Focus Document Fiscal Year Focus Document Period End Date Document Type Entity Central Index Key Entity Common Stock, Shares Outstanding Entity Current Reporting Status Entity Emerging Growth Company Entity Ex Transition Period Entity Filer Category Entity Interactive Data Current Entity Registrant Name Entity Shell Company Entity Small Business ASSETS: Current assets: LIABILITIES AND STOCKHOLDERS’ EQUITY: Current liabilities: Stockholders’ equity: Preferred stock - shares authorized Preferred stock - shares issued Common stock - authorized shares Common stock - shares outstanding Other income (expense): Net (loss) income per common share: Weighted average shares outstanding: Condensed Consolidated Statements of Comprehensive (Loss) Income Other comprehensive income (loss): Unrealized gain (loss) on marketable securities: Cash flows from operating activities: Cash flows from investing activities: Supplemental disclosures of cash flow information: Cash paid during the period for: Cash refunded during the period for: Contribution of stock to 401(k) plan Contribution of stock to 401(k) plan (in Shares) Stock-based compensation expense Exercise of stock options and stock appreciation rights - net of shares tendered for exercise price Exercise of stock options and stock appreciation rights - net of shares tendered for exercise price (in Shares) Opening BS adjustment for adoption of ASU 2014-09 Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Earnings Per Share [Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Weighted average shares outstanding: Effect of dilutive securities Weighted Average Number Diluted Shares Outstanding Adjustment Long-term Contracts or Programs Disclosure [Text Block] Costs and Estimated Earnings in Excess of Billings, Net [Table Text Block] Treasury Stock [Text Block] Inventory Disclosure [Text Block] Schedule of Inventory, Current [Table Text Block] Lessee, Operating Leases [Text Block] Lessee, Operating Lease, Disclosure [Table Text Block] Assets Liabilities Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] 2020 2021 2022 2023 2024 Thereafter Lessee, Operating Lease, Liability, Maturity [Table Text Block] Remainder of 2020 2021 2022 2023 2024 Thereafter Segment Reporting Disclosure [Text Block] Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Revenues: Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Operating (loss) income: Reconciliation of Assets from Segment to Consolidated [Table Text Block] Identifiable assets: Disaggregation of Revenue [Table Text Block] Revenue from External Customers by Products and Services [Table Text Block] Revenues by Product Line: Investment Holdings [Text Block] Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Cost Gross Unrealized Gains Fair Market Value Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block] Fair Value, Less than 12 months Fair Value, 12 Months or more Fair Value April 30, 2019 Investments Classified by Contractual Maturity Date [Table Text Block] Current Due after one year through five years Due after five years through ten years New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Debt Disclosure [Text Block] Income Tax Disclosure [Text Block] Less imputed interest Gross Unrealized Losses Unrealized Losses, Less than 12 months Unrealized Losses, 12 Months or more Unrealized Losses Award Type [Axis] Share-based Payment Arrangement, Option [Member] Change in Accounting Estimate by Type [Axis] Contracts Accounted for under Percentage of Completion [Member] Geographical [Axis] UNITED STATES Investment, Name [Axis] Morion Inc [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Loss on Contracts Defined Contribution Plan, Employer Discretionary Contribution, Shares Operating Leases, Rent Expense Operating Lease, Cost Operating Lease, Weighted Average Remaining Lease Term Operating Lease, Weighted Average Discount Rate, Percent Number of Reportable Segments Number Of Principal Markets Cost Method Investment Ownership Percentage Related Party Transaction, Purchases from Related Party Revenue from Related Parties Due to Related Parties Proceeds from Dividends Received Proceeds from Sale of Debt Securities, Available-for-sale Available-for-sale Securities, Gross Realized Gains Equity Component [Domain] Segments [Domain] Reconciliation of Revenue from Segments to Consolidated [Table] Segment Reporting, Revenue Reconciling Item [Line Items] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Reconciliation of Assets from Segment to Consolidated [Table] Segment Reporting, Asset Reconciling Item [Line Items] Product and Service [Domain] Disaggregation of Revenue [Table] Disaggregation of Revenue [Line Items] Revenue from External Customers by Products and Services [Table] Revenue from External Customer [Line Items] Financial Instruments [Domain] NOTE I - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Schedule of Available-for-sale Securities Reconciliation [Table] NOTE I - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Schedule of Available-for-sale Securities Reconciliation [Line Items] NOTE I - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table] NOTE I - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Line Items] NOTE I - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Investments Classified by Contractual Maturity Date [Table] NOTE I - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Investments Classified by Contractual Maturity Date [Line Items] Award Type [Domain] NOTE B - EARNINGS PER SHARE (Details) [Table] NOTE B - EARNINGS PER SHARE (Details) [Line Items] Change in Accounting Estimate, Type [Domain] NOTE C - COSTS AND ESTIMATED EARNINGS IN EXCESS OF BILLINGS, NET (Details) [Table] NOTE C - COSTS AND ESTIMATED EARNINGS IN EXCESS OF BILLINGS, NET (Details) [Line Items] Geographical [Domain] NOTE E - INVENTORIES (Details) [Table] NOTE E - INVENTORIES (Details) [Line Items] NOTE G - SEGMENT INFORMATION (Details) [Table] NOTE G - SEGMENT INFORMATION (Details) [Line Items] Investment, Name [Domain] NOTE H - INVESTMENT IN MORION, INC. (Details) [Table] NOTE H - INVESTMENT IN MORION, INC. (Details) [Line Items] Carry amount, as of the balance sheet date, of the cash surrender value of life insurance and cash held in trust. The percentage of ownership in the investee accounted for under the cost method of accounting. Tabular disclosure of information pertaining to costs and estimated earnings in excess of billings, net. Number contributions made by an employer to a defined contribution plan. Number of Principal Markets Frequency Electronics Inc New York [Member] Components of an entity that engage in business activities from which they may earn revenue and incur expenses, including transactions with other components of the same entity. Frequency Electronics Inc Zyfer [Member] Components of an entity that engage in business activities from which they may earn revenue and incur expenses, including transactions with other components of the same entity. Government Non Space Revenue [Member] Product or service. Inter Segment [Member] Components of an entity that engage in business activities from which they may earn revenue and incur expenses, including transactions with other components of the same entity. Morion Inc [Member] Name of investment. Other Commercial Industrial Revenue [Member] Product or service. POC Revenue [Member] Type of revenue. POT Revenue [Member] Type of revenue. Satellite Revenue [Member] Product or service. RevenuesByProductLineAbstract NetLossIncomePerCommonShareAbstract SupplementalDisclosuresOfCashFlowInformationAbstract OperatingLossIncomeAbstract NumberOfPrincipalMarkets April302019Abstract CondensedConsolidatedStatementsOfComprehensiveLossIncomeAbstract WeightedAverageSharesOutstandingAbstract0 CashFlowsFromOperatingActivitiesAbstract OtherComprehensiveIncomeLossAbstract WeightedAverageSharesOutstandingAbstract AssetsAbstract0 IdentifiableAssetsAbstract CostMethodInvestmentOwnershipPercentage UnrealizedGainLossOnMarketableSecuritiesAbstract OtherIncomeExpenseAbstract CashFlowsFromInvestingActivitiesAbstract CashPaidDuringThePeriodForAbstract CashRefundedDuringThePeriodForAbstract CostsAndEstimatedEarningsInExcessOfBillingsNetTableTextBlock DefinedContributionPlanEmployerDiscretionaryContributionShares Common Stock, Shares Authorized Operating Lease, Weighted Average Remaining Lease Term Stock Issued During Period, Value, Stock Options Exercised Operating Lease, Cost Entity Registrant Name Disaggregation of Revenue [Table Text Block] Inventory Disclosure [Text Block] Assets, Current [Abstract] Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Stockholders' Equity Attributable to Parent Gross Profit Amendment Flag Earnings Per Share [Text Block] Revenue from Related Parties Available-for-sale Securities, Gross Realized Gains Entity Central Index Key Lessee, Operating Lease, Liability, Payments, Due Year Two Comprehensive Income (Loss), Net of Tax, Attributable to Parent Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Liabilities, Current [Abstract] Cash and Cash Equivalents, at Carrying Value, Including Discontinued Operations Liabilities [Abstract] Available-for-sale Securities, Amortized Cost Basis Proceeds from Income Tax Refunds Entity Shell Company Number of Reportable Segments Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Liabilities and Equity [Abstract] Stock Issued During Period, Value, Employee Benefit Plan Interest Expense Operating Leases, Future Minimum Payments, Due in Four Years Income Tax Disclosure [Text Block] Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Revenue from External Customers by Products and Services [Table Text Block] Operating Leases, Future Minimum Payments, Due Thereafter Reconciliation of Assets from Segment to Consolidated [Table Text Block] Weighted Average Number Diluted Shares Outstanding Adjustment Available-for-sale Securities, Current Lessee, Operating Lease, Disclosure [Table Text Block] Entity Common Stock, Shares Outstanding Cumulative Effect on Retained Earnings, Net of Tax Shares, Outstanding Operating Leases, Future Minimum Payments Due Increase (Decrease) in Operating Capital Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax Payments to Acquire Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Liabilities, Current Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Cash and Cash Equivalents, Period Increase (Decrease) Lessee, Operating Lease, Liability, Maturity [Table Text Block] Operating Leases, Future Minimum Payments, Remainder of Fiscal Year Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Segment Reporting Disclosure [Text Block] Assets, Current Operating Leases, Future Minimum Payments, Due in Five Years Liabilities and Equity Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Lessee, Operating Lease, Liability, Payments, Due Stock Issued During Period, Shares, Employee Benefit Plan Schedule of Inventory, Current [Table Text Block] Entity Small Business Operating Leases, Future Minimum Payments, Due in Two Years Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Entity Filer Category Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Loss on Contracts Preferred Stock, Shares Authorized Proceeds from Dividends Received Revenues [Abstract] Stockholders' Equity Attributable to Parent [Abstract] Assets Treasury Stock, Value Available-for-sale Securities Preferred Stock, Shares Issued Due to Related Parties Document Period End Date Lessee, Operating Leases [Text Block] Other Comprehensive Income (Loss), Net of Tax Net Cash Provided by (Used in) Investing Activities Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block] Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Operating Leases, Future Minimum Payments, Due in Three Years Other Noncash Income (Expense) Document Fiscal Year Focus Lessee, Operating Lease, Liability, Undiscounted Excess Amount Liabilities Document Fiscal Period Focus Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Investments Classified by Contractual Maturity Date [Table Text Block] Contract with Customer, Liability Lessee, Operating Lease, Liability, Payments, Due Year Four Investment Holdings [Text Block] Entity Emerging Growth Company Entity Current Reporting Status Document Type Assets [Abstract] Stockholders' Equity before Treasury Stock Entity Interactive Data Current Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months Contract with Customer, Asset, after Allowance for Credit Loss Long-term Contracts or Programs Disclosure [Text Block] Available-for-sale Securities, Gross Unrealized Gain Lessee, Operating Lease, Liability, Payments, Due after Year Five Available-for-sale Securities, Gross Unrealized Loss Net Cash Provided by (Used in) Operating Activities Current Fiscal Year End Date Operating Leases, Rent Expense Operating Lease, Liability Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Operating Income (Loss) Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Operating Lease, Weighted Average Discount Rate, Percent Debt Disclosure [Text Block] Entity Ex Transition Period Lessee, Operating Lease, Liability, Payments, Due Year Three Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Treasury Stock [Text Block] Proceeds from Sale of Debt Securities, Available-for-sale Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Payments to Acquire Property, Plant, and Equipment Lessee, Operating Lease, Liability, Payments, Due Year Five Common Stock, Shares, Outstanding Related Party Transaction, Purchases from Related Party Statement [Table] Statement [Line Items] Scenario [Axis]