Statement of Financial Position [Abstract] Cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Marketable securities Accounts receivable, net of allowance for doubtful accounts of $189 at January 31, 2016 and April 30, 2015 Allowance for doubtful accounts Costs and estimated earnings in excess of billings, net Net asset Inventories Inventory, Net Deferred and prepaid income taxes Prepaid expenses and other Total current assets Property, plant and equipment, at cost, less accumulated depreciation and amortization Deferred income taxes Goodwill and other intangible assets Cash surrender value of life insurance and cash held in trust Other assets Total assets Identifiable Assets Accounts payable - trade Accrued liabilities Total current liabilities Long term debt- noncurrent Deferred compensation Deferred rent and other liabilities Total liabilities Commitments and contingencies Preferred stock - $1.00 par value Preferred stock, par value Common stock - $1.00 par value, issued 9,164 shares Common stock, par value Common stock shares issued Additional paid-in capital Retained earnings Common stock reacquired and held in treasury - at cost (425 shares at January 31, 2016 and 465 shares at April 30, 2015) Treasury stock, shares Accumulated other comprehensive income Total stockholders' equity Total liabilities and stockholders' equity Income Statement [Abstract] Revenues Revenues Cost of revenues Gross margin Selling and administrative expenses Research and development expenses Operating profit Operating profit (loss) Investment income Interest expense Other income (expense), net Income before provision for income taxes Provision for income taxes Net income Net income Net income Basic (in Dollars per share) Diluted (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 of $226 and ($145) and $76 and $41 Reclassification adjustment for realized gains included in net income, net of tax of $45 and $128 and $45 and $128 Total unrealized (loss) gain on marketable securities, net of tax Total other comprehensive (loss) Comprehensive income Statement of Cash Flows [Abstract] Non-cash charges to earnings Net changes in operating assets and liabilities Net cash provided (used in) by operating activities Proceeds on redemption of marketable securities Proceeds from Sale and Maturity of Marketable Securities Purchase of marketable securities Purchase of fixed assets and other assets Net cash (used in) provided by investing activities Proceeds from credit line borrowings Repayment of credit line borrowings Tax benefit from exercise of stock-based compensation Net cash provided (used in) by financing activities Net increase (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 Interest Income Taxes Disclosure Text Block [Abstract] Earnings Per Share [Abstract] Schedule of Earnings Per Share, Basic and Diluted [Abstract] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [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 Disclosure Text Block Supplement [Abstract] Inventory Disclosure [Abstract] Schedule of Inventory, Current [Abstract] Raw Materials and Component Parts Work in Progress Finished Goods Segment Reporting [Abstract] Reconciliation of Revenue from Segments to Consolidated [Abstract] Segments [Axis] Frequency Electronics Inc New York [Member] Gillam Frequency Electronics Inc [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] Geographical [Axis] CHINA Identifiable assets Investment Holdings [Abstract] Investments, Debt and Equity Securities [Abstract] Schedule of Available-for-sale Securities Reconciliation [Abstract] Eligible Item or Group for Fair Value Option [Axis] Fixed Income Securities [Member] Equity Securities [Member] Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] Investments Classified by Contractual Maturity Date [Abstract] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Debt Disclosure [Abstract] Income Tax Disclosure [Abstract] ASSETS: Current assets: LIABILITIES AND STOCKHOLDERS' EQUITY: Current liabilities: Stockholders' equity: Other income (expense): Net income per common share Weighted average shares outstanding Condensed Consolidated Statements of Comprehensive Income Other comprehensive (loss): Unrealized (loss) gain on marketable securities: Change in market value of marketable securities before reclassification, tax Reclassification adjustment for realized gains included in net income, tax Cash flows from operating activities: Cash flows from investing activities: Cash flows from financing activities: Supplemental disclosures of cash flow information: Cash paid during the period for: 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 Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Outstanding options and SARS excluded 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] 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] 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, 2015 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] Gross Unrealized Losses Unrealized Losses, Less than 12 months Unrealized Losses, 12 Months or more Unrealized Losses Change in Accounting Estimate by Type [Axis] Contracts Accounted for under Percentage of Completion [Member] UNITED STATES BELGIUM Investment [Axis] Morion Inc [Member] Other Commitments [Axis] Licensing Agreement [Member] Products and Services [Axis] Product and Training Services [Member] Related Party Transaction [Axis] Balance for Transfer of License Due Once State Department Approves Removal of Certain Provisions [Member] Credit Facility [Axis] Line of Credit [Member] Debt Instrument [Axis] JP Morgan Chase Bank, N.A. [Member] Long-term Debt, Type [Axis] Debt Instrument, Tranche B [Member] Debt Instrument, Tranche A [Member] Variable Rate [Axis] London Interbank Offered Rate (LIBOR) [Member] Defined Contribution Plan, Employer Discretionary Contribution, Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Number of Reportable Segments Number Of Principal Markets Cost Method Investment Ownership Percentage Related Party Transaction, Purchases from Related Party Revenue from Related Parties Accounts Payable, Related Parties, Current Accounts Receivable, Related Parties, Current Long-term Purchase Commitment, Description License And Equipment Fee Receivable Percentage Of Royalties Payable On Third Party Sales Long-term Purchase Commitment, Period Purchase Commitment, Remaining Minimum Amount Committed Available-for-sale Securities, Gross Realized Gain (Loss) Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Borrowing Capacity, Description Long-term Line of Credit Line of Credit Facility, Collateral Debt Instrument, Basis Spread on Variable Rate Line of Credit Facility, Expiration Date Line of Credit Facility, Commitment Fee Percentage Deferred Tax Assets, Valuation Allowance 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] Geographical [Domain] Reconciliation of Assets from Segment to Consolidated [Table] Segment Reporting, Asset Reconciling Item [Line Items] Fair Value, Option, Eligible Item or Group [Domain] NOTE H - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Schedule of Available-for-sale Securities Reconciliation [Table] NOTE H - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Schedule of Available-for-sale Securities Reconciliation [Line Items] NOTE H - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table] NOTE H - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Line Items] NOTE H - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Investments Classified by Contractual Maturity Date [Table] NOTE H - FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Investments Classified by Contractual Maturity Date [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] NOTE E - INVENTORIES (Details) [Table] NOTE E - INVENTORIES (Details) [Line Items] NOTE F - SEGMENT INFORMATION (Details) [Table] NOTE F - SEGMENT INFORMATION (Details) [Line Items] Investment [Domain] Other Commitments [Domain] Related Party Transaction [Domain] Products and Services [Domain] NOTE G - INVESTMENT IN MORION, INC. (Details) [Table] NOTE G - INVESTMENT IN MORION, INC. (Details) [Line Items] Debt Instrument, Name [Domain] Long-term Debt, Type [Domain] Variable Rate [Domain] Credit Facility [Domain] NOTE J - CREDIT FACILITY (Details) [Table] NOTE J - CREDIT FACILITY (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. Amounts due from investee for license and equipment fee. Number of Principal Markets Percentage of royalties payable on third party sales Balance For Transfer Of License Due Once State Department Approves Removal Of Certain Provisions [Member] Description of transaction with related party. Debt Instrument Tranche A [Member] First portion of debt available for distribution. Debt Instrument Tranche B [Member] Second portion of debt available for distribution. 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. Gillam Frequency Electronics Inc [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. 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. JP Morgan Chase Bank NA [Member] The name for the particular debt instrument or borrowing that distinguishes it from other debt instruments or borrowings, including draws against credit facilities. Licensing Agreement [Member] Other future obligations. Morion Inc [Member] Name of investment. Product And Training Services [Member] Type of product and services. Document and Entity Information [Abstract] Net Cash Provided by (Used in) Operating Activities Net Cash Provided by (Used in) Financing Activities Available-for-sale Securities, Gross Unrealized Loss Entity Public Float Document Period End Date Trading Symbol Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss Document Fiscal Period Focus Entity Current Reporting Status Deferred Tax Assets, Net of Valuation Allowance, Noncurrent Document Type Document Fiscal Year Focus Payments to Acquire Property, Plant, and Equipment Assets Treasury Stock, Value Net Cash Provided by (Used in) Investing Activities Other Comprehensive Income (Loss), Net of Tax Current Fiscal Year End Date Billings in Excess of Cost Available-for-sale Securities Liabilities Other Noncash Income (Expense) Entity Central Index Key Amendment Flag Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Payments to Acquire Marketable Securities Entity Registrant Name Increase (Decrease) in Operating Capital Repayments of Lines of Credit Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss Liabilities and Equity Assets, Current Cash and Cash Equivalents, Period Increase (Decrease) Liabilities, Current Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Entity Common Stock, Shares Outstanding Cash and Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Other Assets Stockholders' Equity Attributable to Parent Gross Profit Entity Voluntary Filers Entity Filer Category Entity Well-known Seasoned Issuer Comprehensive Income (Loss), Net of Tax, Attributable to Parent Interest Expense Amendment Description Statement [Table] Statement [Line Items] Scenario [Axis]