Document And Entity Information us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo Finite-Lived Intangible Assets, Amortization Expense, Year Two Dividend yield us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree Finite-Lived Intangible Assets, Amortization Expense, Year Three Note To Financial Statement Details Textual us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour Finite-Lived Intangible Assets, Amortization Expense, Year Four Note 3 - Inventories us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive Finite-Lived Intangible Assets, Amortization Expense, Year Five Note 4 - Property and Equipment, Net Note 5 - Patents and Trademarks, Net Average risk-free interest rate Note 6 - Investments in Joint Ventures Note 8 - Stockholders' Equity us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months Note 9 - Net Income Per Common Share ntic_AllocatedShareBasedCompensationExpenseEstimateRemainderOfFiscalYear Allocated Share-based Compensation Expense, Estimate Remainder of Fiscal Year Estimated expense to be recognized for the remainder of the fiscal year arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. Note 10 - Stock-based Compensation Note 11 - Segment and Geographic Information ntic_AllocatedShareBasedCompensationExpenseEstimateNextFiscalYear Allocated Share-based Compensation Expense, Estimate, Next Fiscal Year Estimated expense to be recognized for the next fiscal year following the most recent fiscal year arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. Note 13 - Fair Value Measurements Income Tax Disclosure [Text Block] Note 14 - Supplemental Cash Flow Information us-gaap_StockOptionPlanExpense Stock or Unit Option Plan Expense Note 3 - Inventories - Inventories (Details) ntic_AllocatedShareBasedCompensationExpenseEstimateFiscalYearTwo Allocated Share-based Compensation Expense, Estimate, Fiscal Year Two Estimated expense to be recognized for the second fiscal year following the most recent fiscal year arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. Note 4 - Property and Equipment, Net - Components of Property and Equipment, Net (Details) Note 5 - Patents and Trademarks, Net - Patents and Trademarks, Net (Details) us-gaap_OtherAssetsNoncurrent Other us-gaap_ShareBasedCompensation Stock-based compensation Expected volatility us-gaap_LiabilitiesCurrent Total current liabilities Note 6 - Investments in Joint Ventures - Condensed Balance Sheet of EXCOR and All Other Joint Ventures (Details) Note 6 - Investments in Joint Ventures - Condensed Income Statement of EXCOR and All Other Joint Ventures (Details) Title of Individual [Axis] Note 8 - Stockholders' Equity - Schedule of Dividends Payable (Details) us-gaap_FiniteLivedIntangibleAssetUsefulLife Finite-Lived Intangible Asset, Useful Life Relationship to Entity [Domain] Note 9 - Net Income Per Common Share - Reconciliation of the Earnings Per Share Computations (Details) Note 10 - Stock-based Compensation - Black-scholes Option-pricing Model Assumptions (Details) Expected life of option (Year) Inside the USA to Unaffiliated Customers [Member] Inside the USA to Unaffiliated Customers. Note 11 - Segment and Geographic Information - Net Sales by Segment (Details) Note 11 - Segment and Geographic Information - Cost of Goods Sold by Segment (Details) Note 11 - Segment and Geographic Information - Net Sales by Geographic Location (Details) Joint Ventures in Which the Company is a Shareholder Directly and Indirectly Outside the USA [Member] Joint ventures in which the company is a shareholder directly and indirectly outside the USA [member] Unaffiliated Customers Outside the USA [Member] Unaffiliated customers outside the USA [member] Note 11 - Segment and Geographic Information - Fees for Services Provided to Joint Ventures by Geographic Location as a Percentage of Total Fees (Details) Note 11 - Segment and Geographic Information - Total Long-lived Assets by Geographic Distribution (Details) us-gaap_Revenues Total net sales Total net sales us-gaap_AdjustmentForAmortization Amortization expense Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Note 11 - Segment and Geographic Information - Total Net Sales by Geographic Distribution (Details) OPERATING EXPENSES: Note 13 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value Recurring Basis (Details) Note 14 - Supplemental Cash Flow Information - Supplemental Disclosures of Cash Flow Information (Details) Notes To Financial Statements Notes To Financial Statements [Abstract] Fees for Services Provided to Joint Ventures [Member] Represents fees for services provided to joint ventures. ntic_TotalFeesForServicesProvidedToJointVenturesGeographicLocation Fees Total fees for services provided to joint ventures by geographic locations. Schedule of Finite-Lived Intangible Assets [Table Text Block] Deferred Bonus and Profit Sharing Arrangements, Individual Contracts, Type of Deferred Compensation [Axis] Deferred Bonus and Profit Sharing Arrangement, Individual Contract, Type of Deferred Compensation [Domain] OTHER COMPREHENSIVE INCOME (LOSS) – FOREIGN CURRENCY TRANSLATION ADJUSTMENT us-gaap_Depreciation Depreciation expense ntic_EntityWideFeesForServicesProvidedToJointVenturesGeographicPercentage Percentage of total fees Percentage of entity wide fees for services provided to joint ventures generated from geographic location. Intangible Assets Disclosure [Text Block] us-gaap_AssetsCurrent Total current assets Stockholders' Equity Note Disclosure [Text Block] us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest Total equity us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2 Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Income taxes Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Common stock, $0.02 par value per share; authorized 15,000,000 shares as of May 31, 2018 and 10,000,000 shares as of August 31, 2017; issued and outstanding 4,541,304 and 4,535,018, respectively Adjustments to reconcile net income to net cash (used in) provided by operating activities: us-gaap_CommonStockSharesAuthorized Common Stock, Shares Authorized Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Payroll and related benefits Income taxes payable Range [Domain] Maximum [Member] Minimum [Member] Accounts payable Revolving Credit Facility [Member] ZERUST [Member] Represents ZERUST. Product and Service [Axis] NaturTec [Member] Represents NaturTec segment. Product and Service [Domain] Range [Axis] Reconciliation of Cost of Goods Sold from Segments to Consolidated [Table Text Block] Tabular disclosure of all significant reconciling items in the reconciliation of total cost of goods sold from reportable segments to the entity's consolidated revenues. Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Investment, Name [Domain] Deferred income taxes Credit Facility [Axis] Credit Facility [Domain] Preferred stock, no par value; authorized 10,000 shares; none issued and outstanding Cost of Goods Sold Type [Axis] Cost of goods sold type [axis] us-gaap_OtherAccruedLiabilitiesCurrent Other Cost of Goods Sold Type [Domain] Preferred stock, shares issued (in shares) Direct Cost of Goods Sold [Member] Direct cost of goods sold [member] Cash paid for interest Indirect Cost of Goods Sold [Member] Indirect cost of goods sold [member] us-gaap_PolicyTextBlockAbstract Accounting Policies Cash Flow, Supplemental Disclosures [Text Block] Prepaid expenses Investment, Name [Axis] ntic_CostOfGoodsSoldAsPercentageOfProductSales ZERUST® Represents cost of goods sold as percentage of product sales. Preferred stock, par value (in dollars per share) us-gaap_NoncurrentAssets Property and equipment Property, Plant and Equipment Disclosure [Text Block] Geographical [Axis] Property, Plant and Equipment [Table Text Block] Geographical [Domain] Preferred stock, shares authorized (in shares) ntic_PercentageOfIndividualBonusPayoutDeterminedByActualVersusTargetedEBITOIResults Percentage of Individual Bonus Payout Determined by Actual Versus Targeted EBITOI Results Percentage of individual's bonus payout determined based upon the Company's actual EBITOI for the fiscal year compared to pre-established target EBITOI for the fiscal year. Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] us-gaap_InventoryNet Total inventory JOINT VENTURE OPERATIONS: Joint venture operations ntic_PercentageOfIndividualsPayoutDeterminedUponAchievementOfCertainPreEstablishedIndividualPerformanceObjectives Percentage of Individuals Payout Determined Upon Achievement of Certain Pre-Established Individual Performance Objectives Percentage of individual's payout determined based upon achievement of certain pre-established individual performance objectives. ntic_EntityWideTradeJointVentureReceivablesThreeJointVenturesPercentage Entity Wide Trade Joint Venture Receivables, Three Joint Ventures,Percentage Percentage of total trade joint venture receivables accounted for by three joint ventures. WEIGHTED AVERAGE COMMON SHARES ASSUMED OUTSTANDING: Weighted average number of shares outstanding, basic and diluted[abstract] Other Countries [Member] Countries identified as "Other". us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent us-gaap_PaymentsToAcquireIntangibleAssets Additions to patents Fair Value, Inputs, Level 3 [Member] us-gaap_PaymentsToAcquirePropertyPlantAndEquipment Additions to property and equipment us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements Weighted shares assumed upon exercise of stock options (in shares) Accrued liabilities: Fair Value Hierarchy and NAV [Domain] us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Inventories Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1 Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Cash paid for income taxes Fair Value Hierarchy and NAV [Axis] us-gaap_ProceedsFromDividendsReceived Dividends received from joint ventures Reconciliation of Revenue from Segments to Consolidated [Table Text Block] CURRENT LIABILITIES: Vesting [Axis] Vesting [Domain] us-gaap_Assets Total assets PNC Bank [Member] Represents PNC bank. Plan Name [Axis] Plan Name [Domain] us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Non-controlling interest CASH FLOWS FROM OPERATING ACTIVITIES: One Year after Date of Grant [Member] The vesting term that options become exercisable. Statement [Line Items] Trade allowance us-gaap_NumberOfReportableSegments Number of Reportable Segments Receivables: NET SALES: Finite-Lived Intangible Assets by Major Class [Axis] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Finite-Lived Intangible Assets, Major Class Name [Domain] Additional paid-in capital ntic_NumberOfStockBasedCompensationPlans Number of Stock-based Compensation Plans The number of stock-based compensation plans administered by the Compensation Committee of the Board of Directors and the Board of Directors, during the period. Segment Reporting Disclosure [Text Block] CURRENT ASSETS: Cash and cash equivalents us-gaap_NetIncomeLoss NET INCOME ATTRIBUTABLE TO NTIC Net income attributable to NTIC us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization Less accumulated amortization Patents and trademarks, net Patents and trademarkes, net us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss Net income INTEREST INCOME us-gaap_FiniteLivedIntangibleAssetsGross Patents and trademarks OTHER ASSETS: NET INCOME ATTRIBUTABLE TO NON-CONTROLLING INTERESTS us-gaap_NetCashProvidedByUsedInFinancingActivities Net cash used in financing activities us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenue Net sales COMMITMENTS AND CONTINGENCIES (Note 12) us-gaap_EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss Gross profit us-gaap_OtherOperatingIncome Total joint venture operations Joint ventures’ equity OPERATING INCOME Employee Stock Option [Member] us-gaap_NetCashProvidedByUsedInOperatingActivities Net cash (used in) provided by operating activities us-gaap_NetCashProvidedByUsedInInvestingActivities Net cash used in investing activities us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS: us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] us-gaap_GrossProfit Gross profit Cost of goods sold Cost of goods sold us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities Current liabilities us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNoncurrentLiabilities Noncurrent liabilities COMPREHENSIVE INCOME ATTRIBUTABLE TO NON-CONTROLLING INTERESTS us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentAssets Current assets us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssets Total assets EQUITY: Commitments and Contingencies Disclosure [Text Block] us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment Less accumulated depreciation PROPERTY AND EQUIPMENT, NET Net Northern Technologies International Corporation’s share of joint ventures’ equity us-gaap_PropertyPlantAndEquipmentGross Gross us-gaap_MachineryAndEquipmentGross Machinery and equipment us-gaap_Land Land us-gaap_BuildingsAndImprovementsGross Buildings and improvements us-gaap_LettersOfCreditOutstandingAmount Letters of Credit Outstanding, Amount us-gaap_PaymentsOfDividendsMinorityInterest Dividend received by non-controlling interest Condensed Balance Sheet [Table Text Block] us-gaap_AccruedBonusesCurrentAndNoncurrent Accrued Bonuses Condensed Income Statement [Table Text Block] Equity Method Investments and Joint Ventures Disclosure [Text Block] us-gaap_PaymentsOfDividendsCommonStock Dividends paid on NTIC common stock NET INCOME NET INCOME Net income us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest COMPREHENSIVE INCOME ntic_CommonStockAdditionalSharesAuthorized Common Stock, Additional Shares Authorized The additional number of common shares permitted to be issued by an entity's charter and bylaws. CASH FLOWS FROM INVESTING ACTIVITIES: us-gaap_PaymentsForRepurchaseOfCommonStock Repurchase of common stock us-gaap_ProceedsFromStockPlans Proceeds from employee stock purchase plan us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability ntic_ProvisionalAdjustmentsRelatedToTransitionOfTaxOnDeemedRepatriationOfAccumulatedForeignIncome Provisional Adjustments Related to Transition of Tax on Deemed Repatriation of Accumulated Foreign Income Represents the amount of provisional adjustments related to transition of tax on deemed repatriation of accumulated foreign income. Geographic Distribution [Axis] Geographic Distribution [Domain] JP Morgan Chase Bank [Member] Represents information regarding the JP Morgan Chase Bank. NET INCOME ATTRIBUTABLE TO NTIC PER COMMON SHARE: Earnings Per Share [Text Block] Trade excluding joint ventures, less allowance for doubtful accounts of $50,000 at May 31, 2018 and $40,000 at August 31, 2017 Amount due from customers or clients, but not joint ventures, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection. Proceeds from option exercises us-gaap_TreasuryStockAcquiredAverageCostPerShare Treasury Stock Acquired, Average Cost Per Share BRAZIL Trade joint ventures Amounts due from joint ventures, within one year of the balance sheet date (or the normal operating cycle, whichever is longer) for goods or services (including trade receivables) that have been delivered or sold to joint ventures in the normal course of business. us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable Income tax payable Equity in income from joint ventures Northern Technologies International Corporation’s share of equity in income from joint ventures Equity in income from joint ventures Letter of Credit [Member] Investments in joint ventures Fees for services provided to joint ventures Amounts due for royalties and service fees outside of the normal course of business from entities in which the reporting entity shares joint control with another party or group, due within 1 year (or 1 business cycle). INCOME TAX EXPENSE Income Tax Expense (Benefit), Total us-gaap_IncreaseDecreaseInAccruedLiabilities Accrued liabilities Net sales, excluding joint ventures Net sales either directly to end users or to distributors worldwide, but not sales to the reporting entity's joint ventures and not sales by the reporting entity's joint ventures. Net sales, to joint ventures Net sales by the reporting entity to the reporting entity's joint ventures, but not sales by the reporting entity either directly to end users or to distributors or sales by the reporting entity’s joint ventures. Equity Components [Axis] Equity Component [Domain] ntic_FeesForServicesProvidedToJointVentures Fees for services provided to joint ventures Royalties and service fees from transactions directly with the reporting entity's joint ventures outside the normal course of business. CHINA us-gaap_IncreaseDecreaseInAccountsPayable Accounts payable CZECH REPUBLIC GERMANY us-gaap_OperatingExpenses Total operating expenses General and administrative expenses us-gaap_LineOfCredit Long-term Line of Credit, Total FINLAND us-gaap_IncomeLossIncludingPortionAttributableToNoncontrollingInterest INCOME BEFORE INCOME TAX EXPENSE us-gaap_CashAndCashEquivalentsAtCarryingValue CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD CASH AND CASH EQUIVALENTS AT END OF PERIOD FRANCE UNITED KINGDOM Amendment Flag Accounting Policies [Abstract] us-gaap_ComprehensiveIncomeNetOfTax COMPREHENSIVE INCOME ATTRIBUTABLE TO NTIC CASH DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share) Amount (in dollars per share) INDIA Preferred stock, shares outstanding (in shares) Current Fiscal Year End Date us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 Debt Instrument, Basis Spread on Variable Rate us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets Prepaid expenses and other JAPAN Document Fiscal Period Focus ntic_IncreaseDecreaseInTradeReceivablesExcludingJointVentures Trade, excluding joint ventures The net change during the reporting period in amount due within one year (or one business cycle) from customers or clients, but not joint ventures, for the credit sale of goods and services. Document Fiscal Year Focus us-gaap_IncreaseDecreaseInDeferredIncomeTaxes Deferred income taxes ntic_IncreaseDecreaseInTradeReceivablesJointVentures Trade, joint ventures The net change during the reporting period in amount due within one year (or one business cycle) from joint ventures for the credit sale of goods and services that have been delivered or sold to joint ventures in the normal course of business. Document Period End Date Income Statement Location [Axis] ntic_IncreaseDecreaseInFeesReceivableForServicesProvidedToJointVentures Fees for services provided to joint ventures The net change during the reporting period in amount due within one year (or one business cycle) from joint ventures for royalties and service fees outside of the normal course of business. Income Statement Location [Domain] Fiscal 2018 Bonus Plan [Member] Related to the fiscal 2018 bonus plan. KOREA, REPUBLIC OF Document Type Document Information [Line Items] Document Information [Table] Entity Filer Category Debt Instrument [Axis] Entity Current Reporting Status Debt Instrument, Name [Domain] Entity Voluntary Filers Entity Well-known Seasoned Issuer London Interbank Offered Rate (LIBOR) [Member] Segments [Axis] Segments [Domain] Variable Rate [Domain] us-gaap_PaymentsToAcquireAvailableForSaleSecurities Purchase of available for sale securities Proceeds from the sale of available for sale securities us-gaap_IncreaseDecreaseInIncomeTaxesReceivable Income taxes us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Variable Rate [Axis] Diluted (in shares) Diluted – weighted shares outstanding (in shares) Statement of Comprehensive Income [Abstract] Entity Central Index Key Entity Registrant Name Scenario, Forecast [Member] Entity [Domain] Legal Entity [Axis] Statement [Table] Scenario [Axis] Scenario, Unspecified [Domain] Statement of Financial Position [Abstract] Diluted (in dollars per share) Diluted income per share: (in dollars per share) Basic (in shares) Basic – weighted shares outstanding (in shares) Patents and Trademarks [Member] Represents patents and trademarks. Basic (in dollars per share) Basic income per share: (in dollars per share) Available for sale securities us-gaap_AvailableForSaleSecurities Statement of Cash Flows [Abstract] EXCOR [Member] Represents EXCOR. Entity Common Stock, Shares Outstanding (in shares) Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block] Available for sale securities us-gaap_StockRepurchasedAndRetiredDuringPeriodShares Stock Repurchased and Retired During Period, Shares Income Statement [Abstract] All Other [Member] Represents all other joint ventures. POLAND Revenue from External Customers by Geographic Areas [Table Text Block] us-gaap_IncreaseDecreaseInInventories Inventories Trading Symbol Description of New Accounting Pronouncements Not yet Adopted [Text Block] Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans Stock Issued During Period, Shares, Employee Stock Purchase Plans SWEDEN us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period us-gaap_GainLossOnDispositionOfAssets Gain on disposal of assets us-gaap_TableTextBlock Notes Tables us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity Line of Credit Facility, Maximum Borrowing Capacity Executive Officer [Member] ntic_DebtInstrumentCovenantsFixedChargeCoverageRatio Debt Instrument, Covenants, Fixed Charge Coverage Ratio Represents the fixed charge coverage ratio for the debt instrument under the covenant terms. Term Loan and Line of Credit, Agreements, Loan Agreements [Member] Term loan and line of credit, agreements, loan agreements [member] THAILAND Payable date us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Dividends Declared [Table Text Block] CASH FLOWS FROM FINANCING ACTIVITIES: us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Line of Credit Facility, Lender [Domain] Declaration date Record date us-gaap_InventoryRawMaterialsNetOfReserves Production materials Lender Name [Axis] Selling expenses us-gaap_LiabilitiesAndStockholdersEquity Total liabilities and equity us-gaap_InventoryFinishedGoodsNetOfReserves Finished goods UNITED STATES Retained earnings Research and development expenses us-gaap_AssetsNoncurrent Total other assets Accumulated other comprehensive loss Debt Disclosure [Text Block] us-gaap_InterestExpense INTEREST EXPENSE us-gaap_PaymentsToAcquireInterestInJointVenture Payments to Acquire Interest in Joint Venture The 2007 Plan [Member] Represents Northern Technologies International Corporation Amended and Restated 2007 Stock Incentive Plan. Changes in current assets and liabilities: us-gaap_StockholdersEquity Stockholders’ equity us-gaap_DisclosureTextBlockAbstract Notes to Financial Statements Inventory Disclosure [Text Block] Schedule of Inventory, Current [Table Text Block] Class of Stock [Axis] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] ESPP [Member] Represents Northern Technologies International Corporation Employee Stock Purchase Plan (the ESPP). Northern Technologies International Corporation’s dividends received from joint ventures Northern Technologies International Corporation’s dividends received from joint ventures