Document And Entity Information Statistical Measurement [Axis] Note To Financial Statement Details Textual us-gaap_DividendsPayableDateDeclaredDayMonthAndYear Dividends Payable, Date Declared Significant Accounting Policies Provision for income taxes Provision for income taxes Note 3 - Revenue Recognition Non-Rule 10b5-1 Arrangement Terminated [Flag] Note 4 - Earnings Per Share Non-Rule 10b5-1 Arrangement Adopted [Flag] Note 7 - Leases Cost of goods sold and occupancy costs Cost of goods sold and occupancy costs include the cost of inventory sold during the period (net of discounts and allowances), shipping and handling costs, distribution and supply chain costs (including the costs of our bulk food repackaging facility), buying costs, shrink and store occupancy costs. Store occupancy costs include rent payments, common area maintenance and real estate taxes. Depreciation expense included in cost of goods sold relates to depreciation for assets directly used at our bulk food repackaging facility. Trading Arrangements, by Individual [Table] Note 8 - Property and Equipment Store expenses Represents store level expenses, such as salary and benefits, supplies, utilities, depreciation, advertising, bank credit card changes and other related costs associated with operations and purchasing support. Material Terms of Trading Arrangement [Text Block] Note 9 - Other Assets Pre-opening expenses Expenditures associated with opening new locations and relocations which are non-capital in nature and expensed as incurred. Note 10 - Goodwill and Other Intangible Assets Note 11 - Accrued Expenses Note 14 - Segment Reporting Note 3 - Revenue Recognition - Disaggregation of Revenue (Details) Comprehensive Income, Policy [Policy Text Block] Minimum [Member] Note 4 - Earnings Per Share - Basic and Diluted Earnings Per Share (Details) Note 7 - Leases - Lease Costs (Details) Statistical Measurement [Domain] Note 7 - Leases - Lease Costs 2 (Details) Manufactured Product, Other [Member] Maximum [Member] Note 7 - Leases - Additional Information (Details) Internal-Use Software [Member] Represents the internal-use software. Note 7 - Leases - Future Lease Payments (Details) Note 7 - Leases - Lease Income (Details) us-gaap_IncreaseDecreaseInAccountsReceivable Accounts receivable, net Note 7 - Leases - Future Undiscounted Lease Collections (Details) O 2025 Q3 Dividends [Member] Represents the 2025 Q3 dividends. Note 8 - Property and Equipment - Schedule of Property and Equipment (Details) Note 8 - Property and Equipment - Depreciation and Amortization Expense (Details) Note 8 - Property and Equipment - Depreciation and Amortization Expense 2 (Details) Internal-use software in process The amount of internal-use software in process. Note 9 - Other Assets - Summary of Other Assets (Details) Note 10 - Goodwill and Other Intangible Assets - Summary of Goodwill and Other Intangible Assets (Details) Note 11 - Accrued Expenses - Composition of Accrued Expenses (Details) Above Market Leases [Member] Note 14 - Segment Reporting - Schedule of Segment Reporting Information (Details) Notes To Financial Statements Basis of Presentation and Significant Accounting Policies [Text Block] Notes To Financial Statements [Abstract] us-gaap_InterestCostsCapitalized Interest Costs Capitalized Counterparty Name [Axis] Loss on impairment of long-lived assets and store closing costs Represents impairment of long-lived assets and store closing costs. ngvc_IncreaseDecreaseInOperatingLeaseAsset Operating lease assets The increase (decrease) during the reporting period in operating lease asset. Land Improvements [Member] us-gaap_DividendsCash Cash dividends ngvc_LesseeOperatingLeaseLeaseNotYetCommencedMinimumLeasePayments Lessee, Operating Lease, Lease Not yet Commenced, Minimum Lease Payments Amount of lessee's undiscounted obligation for lease payments for operating lease not yet commenced. Land [Member] us-gaap_IncreaseDecreaseInIncomeTaxesReceivable Income tax receivable Lessee, Operating and Finance Leases [Text Block] The entire disclosure for operating and finance leases of lessee. Operating cash flows from operating leases Amount of operating cash inflow (outflow) from operating leases us-gaap_CommonStockDividendsPerShareDeclared Common Stock, Dividends, Per Share, Declared Additional Information Related to Leases [Table Text Block] Tabular disclosure of additional information related to leases. Operating and Finance Lease, Liability, Maturity [Table Text Block] Tabular disclosure of undiscounted cash flows of operating and finance lease liability. Financing cash flows from finance leases Amount of financing cash inflow (outflow) from finance leases. Operating cash flows from finance leases Amount of operating cash inflow (outflow) from finance leases. Weighted Average [Member] us-gaap_IncreaseDecreaseInInventories Merchandise inventory Counterparty Name [Domain] us-gaap_SharesOutstanding Balances (in shares) Balances (in shares) 2029 ngvc_LesseeOperatingAndFinanceLeaseLiabilityPaymentsDueYearThree Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in third fiscal year following latest fiscal year. 2028 ngvc_LesseeOperatingAndFinanceLeaseLiabilityPaymentsDueYearTwo Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in second fiscal year following latest fiscal year. 2026 ngvc_LesseeOperatingAndFinanceLeaseLiabilityPaymentsRemainderOfFiscalYear Amount of lessee's undiscounted obligation for lease payments for operating and finance lease having an initial or remaining lease term in excess of one year due in remainder of fiscal year following latest fiscal year. Letter of Credit [Member] 2030 ngvc_LesseeOperatingAndFinanceLeaseLiabilityPaymentsDueYearFour Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in fourth fiscal year following latest fiscal year. Dividends [Axis] ngvc_LesseeOperatingAndFinanceLeaseLiabilityImputedInterest Less imputed interest Amount of imputed interest related to the operating and finance lease. Dividends [Domain] Segment Reporting [Text Block] ngvc_LesseeOperatingAndFinanceLeaseLiabilityPaymentsDue Total future undiscounted lease payments Amount of lessee's undiscounted obligation for lease payments for operating and finance lease. Noncurrent lease liability Present value of lessee's discounted obligation for lease payments from operating and finance lease, classified as noncurrent. ngvc_OperatingAndFinanceLeaseLiabilityCurrent Less current portion Present value of lessee's discounted obligation for lease payments from operating and finance lease, classified as current. us-gaap_PaymentsForRent Related Party Transaction, Expenses from Transactions with Related Party Total reported lease liability resent value of lessee's discounted obligation for lease payments from operating and finance lease. Award Type [Axis] Segment Reporting [Table Text Block] Adjustments to reconcile net income to net cash provided by operating activities: us-gaap_Liabilities Total liabilities us-gaap_LiabilitiesAndStockholdersEquity Total liabilities and stockholders’ equity us-gaap_AllocatedShareBasedCompensationExpense Share-Based Payment Arrangement, Expense Title and Position [Axis] us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets Prepaid expenses and other assets us-gaap_ShareBasedCompensation Share-based compensation Cash paid for interest on finance lease obligations, net of capitalized interest of $313 and $164, respectively The amount of cash paid during the current period for interest on capital lease finance obligations and capital lease obligations. Subsequent Event [Member] ngvc_NumberOfOperatingLeases Number of Operating Leases Represents the number of operating leases, leased by the entity. us-gaap_IncreaseDecreaseInAccountsPayableTrade Accounts payable Location, Statement of Income, Balance [Axis] us-gaap_PropertySubjectToOrAvailableForOperatingLeaseNet Property and equipment, net – held for rental Changes in operating assets and liabilities: Land us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAccumulatedDepreciation Less accumulated depreciation and amortization Useful life (Year) us-gaap_IncreaseDecreaseInAccruedLiabilities Accrued expenses us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect Net increase (decrease) in cash and cash equivalents Gift Cards [Member] This item represents gift cards sold by the Company. New Accounting Pronouncements, Policy [Policy Text Block] us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Antidilutive Securities, Name [Domain] Statement [Table] Credit Facility [Axis] Credit Facility [Domain] Revolving Credit Facility [Member] Lease assets obtained in exchange for new operating lease obligations Operating leases us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 Debt Instrument, Basis Spread on Variable Rate us-gaap_FinanceLeasePrincipalPayments Finance lease obligation payments us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity Line of Credit Facility, Maximum Borrowing Capacity Goodwill and other intangible assets, net Total goodwill and other intangibles, net Nature of Operations [Text Block] us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity Line of Credit Facility, Remaining Borrowing Capacity srt_StockRepurchaseProgramAuthorizedAmount1 Stock Repurchase Program, Authorized Amount Long-Term Debt, Type [Axis] Product and Service [Domain] Product and Service [Axis] us-gaap_LineOfCredit Long-Term Line of Credit, Total Buildings (Year) Line of Credit [Member] us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue Total future undiscounted operating lease payments Deposits [Member] Finance leases Operating leases Asset Class [Axis] 2027, operating lease us-gaap_OperatingLeaseExpense Operating Lease, Expense 2026, operating lease 2029, operating lease 2028, operating lease Commitments and Contingencies Disclosure [Text Block] Statement [Line Items] 2030, operating lease Common Stock, Shares, Issued (in shares) Common Stock, Shares, Outstanding (in shares) Award Type [Domain] 2030 us-gaap_LessorOperatingLeasePaymentsToBeReceivedFourYears us-gaap_LessorOperatingLeasePaymentsToBeReceived Total future undiscounted lease collections Common Stock, Shares Authorized (in shares) Operating Lease, Lease Income [Table Text Block] 2027 us-gaap_LessorOperatingLeasePaymentsToBeReceivedNextTwelveMonths us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1 Stock Repurchase Program, Remaining Authorized Repurchase Amount us-gaap_OperatingLeaseLeaseIncome Total rental income Operating Remainder of 2026 us-gaap_LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear Schedule of Accrued Liabilities [Table Text Block] 2029 us-gaap_LessorOperatingLeasePaymentsToBeReceivedThreeYears 2028 us-gaap_LessorOperatingLeasePaymentsToBeReceivedTwoYears Leasehold and Building Improvements [Member] This item represents leasehold and building improvements. Common stock, $0.001 par value, 50,000,000 shares authorized, 23,045,851 and 22,954,712 shares issued and outstanding at June 30, 2026 and September 30, 2025, respectively Intangible Asset and Goodwill [Table Text Block] Software hosting arrangement (SaaS) implementation costs us-gaap_HostingArrangementServiceContractImplementationCostCapitalizedAccumulatedAmortization Less accumulated amortization Depreciation of lease assets Variable Proceeds from property insurance settlements Lessor, Operating Lease, Payment to be Received, Maturity [Table Text Block] Accounts payable Total reported finance lease liability us-gaap_PolicyTextBlockAbstract Accounting Policies us-gaap_DisclosureTextBlockAbstract Notes to Financial Statements Amortizable other assets, net us-gaap_TableTextBlock Notes Tables Borrowings under revolving loans Computer Equipment [Member] Finance lease obligations, net of current portion us-gaap_FinanceLeaseLiabilityPaymentsDue Total future undiscounted finance lease payments Finance lease obligations, current portion Less current portion, finance lease us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount Less imputed interest, finance lease 2029, finance lease 2028, finance lease 2030, finance lease Subsequent Events [Text Block] Accrued expenses Total accrued expenses 2027, finance lease Interest on lease liabilities Nonrelated Party [Member] us-gaap_OperatingLeaseImpairmentLoss Operating Lease, Impairment Loss Related Party [Member] Payroll and employee-related expenses 2026, finance lease us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount Less imputed interest, operating lease Operating lease obligations, net of current portion Total reported operating lease liability Operating Lease, Liability us-gaap_OtherAccruedLiabilitiesCurrent Other Operating lease obligations, current portion Operating Lease, Liability, Current Less current portion, operating lease Co-PACE Financing, current portion Co-PACE Financing Proceeds from sale of property and equipment Standby Letters of Credit [Member] Statement of Stockholders' Equity [Abstract] Intangible Asset, Finite-Lived, Class [Axis] Intangible Asset, Finite-Lived, Class [Domain] Statement of Cash Flows [Abstract] Stockholders’ equity: Long-Term Debt, Type [Domain] ngvc_EarlyLeaseRelocationExpense Early Lease Relocation Expense The amount of early lease relocation expense. Equity Components [Axis] Thereafter, finance lease Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid after fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Operating lease liabilities 2027 ngvc_LesseeOperatingAndFinanceLeaseLiabilityPaymentsDueYearOne Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due in first fiscal year following latest fiscal year. Equity Component [Domain] Federal Funds Rate [Member] Represents the federal funds rate. Thereafter ngvc_LesseeOperatingAndFinanceLeaseLiabilityPaymentsDueAfterYearFour Amount of lessee's undiscounted obligation for lease payments for operating and finance lease, due after fourth fiscal year following latest fiscal year. Equity [Text Block] Additional Paid-in Capital [Member] Construction in process Retained Earnings [Member] us-gaap_PropertyPlantAndEquipmentExcludingLessorAssetUnderOperatingLeaseAfterAccumulatedDepreciation Property and equipment, net – held and used ngvc_PropertyPlantAndEquipmentAdditionsReclassificationOfFinanceLeaseAssets Property, Plant and Equipment, Additions, Reclassification of Finance Lease Assets Amount of reclassification of finance lease assets into long-lived, physical assets used in the normal conduct of business and not intended for resale. ngvc_OperatingLeaseLiabilityIncreaseDecreaseInPeriodPurchasesOfPreviousLeases Operating Lease Liability, Increase (Decrease) in Period, Purchases of Previous Leases The increase (decrease) of the present value of lessee's discounted obligation for lease payments from operating lease resulting from purchases of previous leases. ngvc_PropertyPlantAndEquipmentAdditionsReclassificationOfOperatingLeaseAssets Property, Plant and Equipment, Additions, Reclassification of Operating Lease Assets Amount of reclassification of operating lease assets into long-lived, physical assets used in the normal conduct of business and not intended for resale. ngvc_FinanceLeaseLiabilityIncreaseDecreaseInPeriodPurchasesOfPreviousLeases Finance Lease Liability, Increase (Decrease) in Period, Purchases of Previous Leases The amount of increase (decrease) to the present value of lessee's discounted obligation for lease payments from finance lease during the period resulting from the purchase of previous leases. Property and equipment, net Total property and equipment, net Acquisition of property and equipment not yet paid O 2026 Q1 Dividends [Member] Represents ordinary dividends in the first quarter of 2026. Subsequent Event Type [Domain] Subsequent Event Type [Axis] Furniture and Fixtures [Member] Intangible Asset and Goodwill [Text Block] Deferred income tax liabilities, net Accounts Payable and Accrued Liabilities Disclosure [Text Block] Supplemental disclosures of cash flow information: Current liabilities: us-gaap_LiabilitiesCurrent Total current liabilities us-gaap_LettersOfCreditOutstandingAmount Letters of Credit Outstanding, Amount Secured Overnight Financing Rate (SOFR) [Member] Accounts receivable, net Income taxes paid Lease, Cost [Table Text Block] us-gaap_PaymentsToAcquireIntangibleAssets Acquisition of other intangibles us-gaap_GainLossOnSaleOfPropertyPlantEquipment (Gain) loss on disposal of property and equipment Long-Term Debt [Text Block] Accumulated amortization Merchandise inventory Administrative expenses Depreciation and Amortization Expense [Table Text Block] Tabular disclosure of the allocation of depreciation and amortization expense to a given line item on the income statement for the period. us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest Income before income taxes Additional paid-in capital ngvc_LineOfCreditFacilityRestrictedPaymentCapacity Line of Credit Facility, Restricted Payment Capacity Represents the amount of restricted payment capacity on a line of credit facility. us-gaap_DebtInstrumentAnnualPrincipalPayment Debt Instrument, Annual Principal Payment Segment Reporting, Policy [Policy Text Block] Prepaid expenses and other current assets Use of Estimates, Policy [Policy Text Block] Other Assets Disclosure [Text Block] us-gaap_PaymentsToAcquirePropertyPlantAndEquipment Acquisition of property and equipment Share-based compensation us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation us-gaap_DebtInstrumentCarryingAmount Long-Term Debt, Gross us-gaap_DebtInstrumentFaceAmount Debt Instrument, Face Amount Schedule of Other Assets [Table Text Block] Current assets: us-gaap_AssetsCurrent Total current assets us-gaap_GrossProfit Gross profit Leases, Acquired-in-Place [Member] Issuance of common stock (in shares) Restricted Stock Units (RSUs) [Member] us-gaap_StockRepurchaseProgramPeriodInForce1 Stock Repurchase Program, Period in Force (Year) Debt Instrument, Name [Domain] us-gaap_DebtInstrumentInterestRateStatedPercentage Debt Instrument, Interest Rate, Stated Percentage Trademarks [Member] Related and Nonrelated Parties [Axis] us-gaap_DebtInstrumentPeriodicPayment Debt Instrument, Periodic Payment Debt Instrument [Axis] Operating activities: Investing activities: us-gaap_NetCashProvidedByUsedInOperatingActivities Net cash provided by operating activities Financing activities: us-gaap_NetCashProvidedByUsedInInvestingActivities Net cash used in investing activities us-gaap_NetCashProvidedByUsedInFinancingActivities Net cash (used in) provided by financing activities us-gaap_InterestExpenseDebtExcludingAmortization Interest Expense, Debt, Excluding Amortization Accounting Policies [Abstract] Segments [Domain] Segments [Axis] FTVC, LLC [Member] The entity of FTVC, LLC. Other assets: us-gaap_StockRepurchasedDuringPeriodShares Stock Repurchased During Period, Shares Income Statement [Abstract] Other Intangible Assets [Member] us-gaap_NumberOfReportableSegments Number of Reportable Segments us-gaap_OtherAssetsMiscellaneousNoncurrent Other Deferred income tax expense (benefit) us-gaap_TreasuryStockCommonShares Treasury Stock, Common, Shares Accrued property, sales and use tax payable Carrying value as of the balance sheet date of obligations incurred through that date and payable for accrued income, property, sales and use tax. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Net income Net income Net income us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic us-gaap_DividendsPayableDateOfRecordDayMonthAndYear Dividends Payable, Date of Record Deferred lease and sublease income, net Non-cash interest expense Term Loan [Member] This item represents the term loan. us-gaap_OtherNoncashIncomeExpense Other ngvc_CapitalAndFinancingLeaseObligationsNumberOfLeases Capital and Financing Lease Obligations Number of Leases Represents the number of leases under capital and financing lease obligations. Income Tax Disclosure [Text Block] Restricted Stock [Member] us-gaap_PropertyPlantAndEquipmentExcludingLessorAssetUnderOperatingLeaseAccumulatedDepreciation Less accumulated depreciation and amortization Supplemental disclosures of non-cash investing and financing activities: Related and Nonrelated Parties [Domain] O 2025 Q1 Dividends [Member] The Q1 dividends for the 2025 fiscal year. Related Party Transactions Disclosure [Text Block] us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1 Intangible Asset, Finite-Lived, Remaining Amortization Period Capitalized interest O 2026 Q3 Dividends [Member] Represents O 2026 Q3 Dividends. us-gaap_RepaymentsOfLinesOfCredit Repayments under revolving loans Statement of Financial Position [Abstract] us-gaap_DividendPayableDateToBePaidDayMonthAndYear Dividends Payable, Date to be Paid us-gaap_LiabilitiesNoncurrent Total long-term liabilities Finance leases (Year) Long-term liabilities: Chalet [Member] This item represents the lease agreements with Chalet Properties, LLC Isely Family Land Trust LLC [Member] This item represents property leased from Isely Family Land Trust LLC. Other assets Deferred revenue The amount of accrued liability for gift cards classified as deferred revenue. dei_DocumentType Document Type Document Information [Line Items] Document Quarterly Report us-gaap_LesseeOperatingLeaseTermOfContract Lessee, Operating Lease, Term of Contract us-gaap_LesseeOperatingLeaseRenewalTerm Lessee, Operating Lease, Renewal Term Deferred Financing Costs [Member] Represents the deferred financing costs. Operating leases (Year) Document Information [Table] Co-PACE Financing [Member] Represents the Co-PACE financing. us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) Other [Member] In reference to an asset classified as other. Antidilutive Securities [Axis] Effect of dilutive securities (in shares) dei_EntityInteractiveDataCurrent Entity Interactive Data Current Document Transition Report Weighted average number of shares of common stock outstanding: us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding Diluted (in shares) Weighted average number of shares of common stock outstanding including the effect of dilutive securities (in shares) Direct operating costs Deferred Rent Receivables [Member] In reference to the amount of excess of rental income recognized over rental payment required by lease. Net income per share of common stock: Intangible Asset, Indefinite-Lived, Class [Domain] Weighted average number of shares of common stock outstanding (in shares) Basic (in shares) Software hosting arrangement (SaaS) implementation costs (Year) Useful life of other noncurrent assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Basic (in dollars per share) Basic earnings per share (in dollars per share) Intangible Asset, Indefinite-Lived, Class [Axis] Title and Position [Domain] Deposits Total other intangibles, net Acquired Tenant Lease Intangibles [Member] Represents the Acquired Tenant Lease Intangibles ngvc_WeightedAveragePeriodPriorToCommencementOfRenewalOption Weighted Average Period Prior To Commencement of Renewal Option The weighted average period prior to the commencement of renewal option Tenant lease intangibles acquired in exchange for assumed Co-PACE Financing The amount of intangible assets acquired through debt issuance. Building and land acquired in exchange for assumed Co-PACE Financing The amount of capital expenditures incurred through debt issuance. Internal-use software, net Intangible Asset, Finite-Lived, after Accumulated Amortization Document Fiscal Period Focus finite life intangible asset, gross Document Fiscal Year Focus Amendment Flag Common Stock [Member] us-gaap_SubleaseIncome Sublease income ngvc_OperatingLeaseLiabilityWriteoff Operating Lease, Liability, Write-off Represents write-off operating lease liability. Trademarks Goodwill ngvc_PolicyTable dei_DocumentPeriodEndDate Document Period End Date Building [Member] Property, Plant, and Equipment [Text Block] Long-Lived Asset, Class [Domain] Variable lease cost Legal Entity [Axis] ngvc_AssetsNoncurrentExcludingPropertyPlantAndEquipment Total other assets In reference to the total of noncurrent assets that excludes property plant and equipment. Operating lease cost Short-term lease cost us-gaap_LeaseCost Total lease cost Construction in Progress [Member] dei_EntityFileNumber Entity File Number Entity Tax Identification Number Disaggregation of Revenue [Table Text Block] Entity [Domain] Entity Central Index Key Lease assets obtained in exchange for new finance lease obligations Finance leases Amount of increase (decrease) in right-of-use asset obtained in exchange for finance lease liability. dei_EntityRegistrantName Entity Registrant Name dei_EntityCurrentReportingStatus Entity Current Reporting Status Entity Incorporation, State or Country Code Current Fiscal Year End Date Fair Value Measurement, Policy [Policy Text Block] Entity Filer Category dei_EntityShellCompany Entity Shell Company ngvc_LineOfCreditFacilityDividendRestrictionsMaximumAmount Line of Credit Facility, Dividend Restrictions, Maximum Amount The maximum cash dividends to be paid as required by the terms of the credit facility. Entity Emerging Growth Company us-gaap_OtherComprehensiveIncomeLossNetOfTax Other Comprehensive Income (Loss), Net of Tax Entity Small Business us-gaap_OperatingIncomeLoss Operating income Former CFO [Member] The former CFO. Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] O 2025 Q2 Dividends [Member] Represents the Q2 dividends of 2025. Interest expense, net Interest expense, net us-gaap_ContractWithCustomerLiabilityRevenueRecognized Contract with Customer, Liability, Revenue Recognized Other segment items Entity Address, State or Province Entity Address, City or Town Retained earnings Entity Address, Address Line One us-gaap_GainOnBusinessInterruptionInsuranceRecovery Gain on Business Interruption Insurance Recovery dei_CityAreaCode City Area Code us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation Payments on withholding tax for restricted stock unit vesting dei_LocalPhoneNumber Local Phone Number Entity Address, Postal Zip Code Revenue from Contract with Customer [Text Block] Title of 12(b) Security Security Exchange Name Trading Symbol Class of Stock [Axis] Variable Rate [Axis] Variable Rate [Domain] dei_EntityCommonStockSharesOutstanding Entity Common Stock, Shares Outstanding (in shares) Earnings Per Share [Text Block] Thereafter, operating lease Amount of lessee's undiscounted obligation for lease payment for operating lease due after fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Accrued marketing expenses ngvc_RelatedPartyTransactionNumberOfOwnersThatAreNonIndependentBoardMembersOfTheEntity Related Party Transaction Number of Owners That Are Non-Independent Board Members of the Entity Represents the number of owners of the related party entity that are non-independent board members of the reporting entity. Common stock, par value (in dollars per share) Net sales, percent The amount of revenue, represented as a percentage of total revenue. Long-Lived Asset, Class [Axis] us-gaap_Assets Total assets Cash and cash equivalents Grocery [Member] This item represents grocery products sold by the Company. Dietary Supplements [Member] This item represents the dietary supplement products sold by the Company. Diluted (in dollars per share) Diluted earnings per share (in dollars per share) us-gaap_ContractWithCustomerLiability Contract with Customer, Liability, Total Acquired Above Market Leases [Member] Represents Above Market Leases. O 2026 Q4 Dividends [Member] Represents O 2026 Q4 Dividends. Depreciation and amortization expense Depreciation and amortization Single Reportable Segment [Member] Represents single reportable segment. Asset Class [Domain] Consolidation, Policy [Policy Text Block] Cash paid for interest The New Credit Facility [Member] Refers to information regarding the new credit facility to replace the old credit facility on 2016-01-27 after amounts owed were paid in full. This credit facility is secured by the company's assets and is guaranteed by the entity's holding company and VC Two. Thereafter ngvc_LessorOperatingLeasePaymentToBeReceivedAfterYearFive Amount of lease payment to be received by lessor for operating lease after fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). us-gaap_NumberOfStatesInWhichEntityOperates Number of States in which Entity Operates O 2026 Q2 Dividends [Member] Represents ordinary dividends in Q2 of 2026. us-gaap_StockholdersEquity Total stockholders’ equity Balances Balances us-gaap_PaymentsOfDividendsCommonStock Dividends to shareholders Nature of Operation, Product Information, Concentration of Risk [Table] Finance lease assets, net Operating lease assets, net Operating Lease, Right-of-Use Asset us-gaap_NumberOfStores Number of Stores Net sales Rule 10b5-1 Arrangement Terminated [Flag] Property, Plant, and Equipment [Table Text Block] Rule 10b5-1 Arrangement Adopted [Flag]