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Accounts payable and accrued expenses nvec_AvailableForSaleSecuritiesDebtMaturitiesAfterThreeThroughFiveYearsFairValue 83,956,776 Fair value of available-for-sale debt securities maturing after three through five years. 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Statement of Financial Position [Abstract] us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities Excess tax benefits Stock-based compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Quarterly Financial Information [Text Block] nvec_NumberOfCorporateBondsResultedInLoss Number of Corporate Bonds Resulted in Loss The number of corporate bonds which resulted in a loss. nvec_NumberOfCorporateBonds Number of Corporate Bonds Total number of the entity's portfolio bonds. us-gaap_AvailableForSaleSecuritiesDebtSecurities Total Available-for-sale Securities, Debt Securities INVESTING ACTIVITIES Entity Well-known Seasoned Issuer nvec_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughThreeYearsFairValue 83,956,776 Fair value of available-for-sale debt securities maturing in one to three years. 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4,844,845 issued and outstanding as of September 30, 2015 and 4,857,953 issued and outstanding as of March 31, 2015 Investment Type [Axis] Class of Stock [Axis] Common stock, shares issued (in shares) us-gaap_StockRepurchaseProgramAuthorizedAmount1 Stock Repurchase Program, Authorized Amount Accounting Policies [Abstract] Common stock, shares authorized (in shares) us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1 Stock Repurchase Program, Remaining Authorized Repurchase Amount New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Schedule of Weighted Average Number of Shares [Table Text Block] us-gaap_IncreaseDecreaseInAccountsReceivable Accounts receivable Common stock, par value (in dollars per share) Revenue Inventories Total inventories Municipal Bonds [Member] us-gaap_TreasuryStockSharesAcquired Treasury Stock, Shares, Acquired us-gaap_Revenues Total revenue Common stock, shares outstanding (in shares) Unrealized loss from marketable securities, net of tax Expenses us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue Less Than 1 Year Investments [Domain] Schedule of Inventory, Current [Table Text Block] Inventory Disclosure [Text Block] us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue Fair market value less than 12 months us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue Total Fair Market Value Finished goods Work in process us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets Prepaid expenses and other assets Cash dividends declared per common share (in dollars per share) us-gaap_OperatingExpenses Total expenses us-gaap_PaymentsToAcquirePropertyPlantAndEquipment Purchases of fixed assets Statement [Line Items] us-gaap_Assets Total assets Raw materials Additional paid-in capital Shareholders’ equity us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAggregateLosses Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss Total Gross Unrealized Losses us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses Gross unrealized losses less than 12 months Current liabilities Entity Registrant Name Schedule of Unrealized Loss on Investments [Table Text Block] us-gaap_PropertyPlantAndEquipmentNet Net fixed assets Entity Central Index Key us-gaap_PaymentsToAcquireMarketableSecurities Purchases of marketable securities us-gaap_GrossProfit Gross profit Cost of sales us-gaap_PropertyPlantAndEquipmentGross Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Less accumulated depreciation Long-term deferred tax liabilities Leasehold improvements Entity Common Stock, Shares Outstanding (in shares) Machinery and equipment Earnings Per Share [Text Block] nvec_StockRepurchaseProgramAuthorizedAdditionalAmount Stock Repurchase Program Authorized Additional Amount Amount of additional stock repurchase plan authorized. Fixed assets Non-employee Director Stock Options [Member] An arrangement whereby a non-employee director is issued automatic stock options on their election or reelection to the company's Board. Deferred tax assets Trading Symbol Scenario [Axis] Scenario, Unspecified [Domain] Equity Component [Domain] Equity Components [Axis] us-gaap_AssetsCurrent Total current assets us-gaap_PolicyTextBlockAbstract Accounting Policies Corporate Bond Securities [Member] us-gaap_OperatingIncomeLoss Income from operations Interest income us-gaap_DisclosureTextBlockAbstract Notes to Financial Statements