Statement of Financial Position [Abstract] Cash and cash equivalents Marketable securities Accounts receivable, net of allowance for doubtful accounts of $183 at October 31, 2020 and April 30, 2020 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 Total current assets Property, plant and equipment, at cost, net of accumulated depreciation and amortization Goodwill Cash surrender value of life insurance Other assets Right-of-Use assets – operating leases Operating lease ROU assets Total assets Identifiable Assets Identifiable Assets Accounts payable – trade Accrued liabilities Loss provision accrual Operating lease liability Operating lease liabilities (short-term) Less current obligations under leases Total current liabilities Deferred compensation Operating lease liability – non-current Operating lease liabilities (long-term) Long-term lease obligations Other liabilities 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, 9,176 shares issued and 9,175 shares outstanding at October 31, 2020; 9,164 shares issued and 9,121 shares outstanding at April 30, 2020 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 (1 share at October 31, 2020 and 43 shares at April 30, 2020) 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 (loss) Selling and administrative expenses Research and development expenses Operating (loss) income Operating profit (loss) Investment income Interest expense Other income (expense), net Income (loss) before provision for income taxes Provision for income taxes Net income (loss) Net income (loss) Basic and diluted earnings (loss) per share (in Dollars per share) 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 (loss) gain on marketable securities, net of tax Comprehensive income (loss) Statement of Cash Flows [Abstract] Non-cash charges to earnings Net changes in operating assets and liabilities Net cash provided by 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 cash used in financing activities 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 Statement of Stockholders' Equity [Abstract] Balance (in Shares) Balance (in Shares) Equity Components [Axis] Accounting Policies [Abstract] Earnings Per Share [Abstract] Schedule of Earnings Per Share, Basic and Diluted [Abstract] Diluted EPS Shares outstanding Diluted (in Shares) 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 Disclosure Text Block [Abstract] Lessee, Operating Lease, Disclosure [Abstract] Total lease liabilities Present value of future lease payments Lessee, Operating Lease, Liability, Maturity [Abstract] Total lease payments Segment Reporting [Abstract] Reconciliation of Revenue from Segments to Consolidated [Abstract] Segments [Axis] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract] Schedule of Reconciliation of Assets from Segment to Consolidated [Abstract] Disaggregation of Revenue [Abstract] Product and Service [Axis] Revenue from External Customers by Products and Services [Abstract] Investment Holdings [Abstract] Investments, Debt and Equity Securities [Abstract] Schedule of Available-for-sale Securities Reconciliation [Abstract] Financial Instrument [Axis] Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] Investments Classified by Contractual Maturity Date [Abstract] Accounting Standards Update and Change in Accounting Principle [Abstract] Debt Disclosure [Abstract] Income Tax Disclosure [Abstract] Commitments and Contingencies 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 Filer Category Entity Interactive Data Current Entity Registrant Name Entity Shell Company Entity Small Business ASSETS: Current assets: LIABILITIES AND STOCKHOLDERS’ EQUITY: Current liabilities: Line of credit Current debt Deferred taxes Stockholders’ equity: Preferred stock - shares authorized Preferred stock - shares issued Common stock - authorized shares Common stock - shares outstanding Other income (expense): Net income (loss) per common share: Weighted average shares outstanding: Basic (in Shares) Basic EPS Shares outstanding (weighted average) Condensed Consolidated Statements of Comprehensive Income (Loss) Unrealized gain (loss) on marketable securities: Cash flows from operating activities: Cash flows from investing activities: Net cash used in financing activities: Proceeds from UBS line of credit 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) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Other comprehensive income, net of tax Repayment of PPP Loan Common Stock [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Treasury Stock [Member] AOCI Attributable to Parent [Member] 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 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 Lessee, Operating Lease, Liability, Maturity [Table Text Block] Remainder of 2021 2022 2023 2024 2025 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 profit (loss): 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 Investments Classified by Contractual Maturity Date [Table Text Block] Current Due after one year through five years Due after five years Accounting Standards Update and Change in Accounting Principle [Text Block] Debt Disclosure [Text Block] Income Tax Disclosure [Text Block] Commitments and Contingencies Disclosure [Text Block] Less imputed interest Gross Unrealized Losses Unrealized Losses, Less than 12 months Unrealized Losses, 12 Months or more Unrealized Losses Frequency Electronics Inc New York [Member] Frequency Electronics Inc Zyfer [Member] Inter Segment [Member] Corporate Segment [Member] POC Revenue [Member] POT Revenue [Member] Satellite Revenue [Member] Government Non-Space Revenue [Member] Other Commercial & Industrial Revenue [Member] Fixed Income Securities [Member] Change in Accounting Estimate by Type [Axis] Geographical [Axis] Investment, Name [Axis] Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Loss on Contracts Operating Leases, Rent Expense 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 Cost Method Investments Related Party Transaction, Purchases from Related Party Revenue from Related Parties Proceeds from Dividends Received Proceeds from Sale of Debt Securities, Available-for-sale Available-for-sale Securities, Gross Realized Gains Long-term Line of Credit Loans Payable to Bank Contracts Accounted for under Percentage of Completion [Member] UNITED STATES Morion Inc [Member] 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] FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Schedule of Available-for-sale Securities Reconciliation [Table] FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Schedule of Available-for-sale Securities Reconciliation [Line Items] FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table] FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Line Items] FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Investments Classified by Contractual Maturity Date [Table] FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Investments Classified by Contractual Maturity Date [Line Items] Change in Accounting Estimate, Type [Domain] COSTS AND ESTIMATED EARNINGS IN EXCESS OF BILLINGS, NET (Details) [Table] COSTS AND ESTIMATED EARNINGS IN EXCESS OF BILLINGS, NET (Details) [Line Items] Geographical [Domain] INVENTORIES (Details) [Table] INVENTORIES (Details) [Line Items] SEGMENT INFORMATION (Details) [Table] SEGMENT INFORMATION (Details) [Line Items] Investment, Name [Domain] INVESTMENT IN MORION, INC. (Details) [Table] 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 of Principal Markets 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. 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. Product or service. 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. Name of investment. Product or service. Type of revenue. Type of revenue. Product or service. AssetsAbstract0 IdentifiableAssetsAbstract FrequencyElectronicsIncZyferMember CostMethodInvestmentOwnershipPercentage UnrealizedGainLossOnMarketableSecuritiesAbstract MorionIncMember SatelliteRevenueMember NetCashUsedInFinancingActivitiesAbstract OtherIncomeExpenseAbstract CashFlowsFromInvestingActivitiesAbstract OtherCommercialIndustrialRevenueMember CashPaidDuringThePeriodForAbstract CashRefundedDuringThePeriodForAbstract POTRevenueMember CondensedConsolidatedStatementsOfComprehensiveIncomeLossAbstract CostsAndEstimatedEarningsInExcessOfBillingsNetTableTextBlock POCRevenueMember NetIncomeLossPerCommonShareAbstract RevenuesByProductLineAbstract SupplementalDisclosuresOfCashFlowInformationAbstract NumberOfPrincipalMarkets GovernmentNonSpaceRevenueMember InterSegmentMember WeightedAverageSharesOutstandingAbstract0 CashFlowsFromOperatingActivitiesAbstract FrequencyElectronicsIncNewYorkMember OperatingProfitLossAbstract WeightedAverageSharesOutstandingAbstract Comprehensive Income (Loss), Net of Tax, Attributable to Parent Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Liabilities, Current [Abstract] Entity Registrant Name Treasury Stock [Member] Cash and Cash Equivalents, at Carrying Value, Including Discontinued Operations Liabilities [Abstract] Proceeds from Income Tax Refunds Available-for-sale Securities, Amortized Cost Basis Number of Reportable Segments Deferred Income Tax Liabilities, Net Amendment Flag Liabilities and Equity [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Stock Issued During Period, Value, Employee Benefit Plan Entity Central Index Key Loans Payable to Bank Interest Expense AOCI Attributable to Parent [Member] Operating Leases, Future Minimum Payments, Due in Four Years Income Tax Disclosure [Text Block] Common Stock, Shares Authorized Fixed Income Securities [Member] Line of Credit, Current Operating Lease, Weighted Average Remaining Lease Term Stock Issued During Period, Value, Stock Options Exercised Inventory Disclosure [Text Block] Disaggregation of Revenue [Table Text Block] Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Assets, Current [Abstract] Entity Shell Company Earnings Per Share [Text Block] Stockholders' Equity Attributable to Parent Gross Profit Revenue from Related Parties Long-term Line of Credit Available-for-sale Securities, Gross Realized Gains Liabilities, Current Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Lessee, Operating Lease, Liability, Maturity [Table Text Block] Operating Leases, Future Minimum Payments, Remainder of Fiscal Year Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Assets, Current Segment Reporting Disclosure [Text Block] Liabilities and Equity Operating Leases, Future Minimum Payments, Due in Five Years Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Stock Issued During Period, Shares, Employee Benefit Plan Entity Common Stock, Shares Outstanding Schedule of Inventory, Current [Table Text Block] Operating Leases, Future Minimum Payments, Due in Two Years Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] 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] Accounting Standards Update and Change in Accounting Principle [Text Block] Weighted Average Number of Shares Outstanding, Diluted Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Revenue from External Customers by Products and Services [Table Text Block] Long-term Debt, Current Maturities 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 Small Business Entity Filer Category Shares, Outstanding Operating Leases, Future Minimum Payments Due Commitments and Contingencies Disclosure [Text Block] OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Payments to Acquire Marketable Securities Increase (Decrease) in Operating Capital 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 Lessee, Operating Lease, Liability, Undiscounted Excess Amount Other Noncash Income (Expense) Operating Leases, Future Minimum Payments, Due in Three Years Liabilities Investments Classified by Contractual Maturity Date [Table Text Block] Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Document Period End Date Investment Holdings [Text Block] Contract with Customer, Liability Weighted Average Number of Shares Outstanding, Basic Stockholders' Equity before Treasury Stock Assets [Abstract] Loss on Contracts Preferred Stock, Shares Authorized Proceeds from Dividends Received Document Fiscal Year Focus Assets Treasury Stock, Value Stockholders' Equity Attributable to Parent [Abstract] Revenues [Abstract] Document Fiscal Period Focus Retained Earnings [Member] Preferred Stock, Shares Issued Available-for-sale Securities Entity Emerging Growth Company Entity Current Reporting Status Document Type Other Comprehensive Income (Loss), Net of Tax Entity Interactive Data Current Lessee, Operating Leases [Text Block] Net Cash Provided by (Used in) Investing Activities Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Treasury Stock [Text Block] Common Stock [Member] Cost Method Investments Proceeds from Sale of Debt Securities, Available-for-sale Repayments of Debt Current Fiscal Year End Date Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Additional Paid-in Capital [Member] Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Proceeds from Lines of Credit Payments to Acquire Property, Plant, and Equipment Common Stock, Shares, Outstanding Related Party Transaction, Purchases from Related Party Contract with Customer, Asset, after Allowance for Credit Loss Contracts Accounted for under Percentage of Completion [Member] Long-term Contracts or Programs Disclosure [Text Block] Corporate Segment [Member] Available-for-sale Securities, Gross Unrealized Gain Net Cash Provided by (Used in) Operating Activities Net Cash Provided by (Used in) Financing Activities Available-for-sale Securities, Gross Unrealized Loss Operating Leases, Rent Expense Operating Lease, Liability Operating Income (Loss) Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss UNITED STATES Debt Disclosure [Text Block] Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Operating Lease, Weighted Average Discount Rate, Percent Statement [Table] Statement [Line Items] Scenario [Axis]