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Represents the number of properties leased by the entity.

No definition available.

Name:	ngvc_NumberOfPropertiesLeased
Namespace Prefix:	ngvc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount of the high end of required minimum rental payments per each lease agreement for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

No definition available.

Name:	ngvc_OperatingLeasesFutureMinimumPaymentsDuePerLeaseAgreementHighEndOfRange
Namespace Prefix:	ngvc_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of the low end of required minimum rental payments per each lease agreement for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

No definition available.

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Period Type:	instant

Represents the amount of rent expenditures associated with opening new locations and relocations, which are noncapital in nature and expensed as incurred for stores that are yet not opened.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Period Type:	instant

Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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For a classified balance sheet, the cumulative difference between the rental income or payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense, by the lessor or lessee, respectively, more than one year after the balance sheet date.

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This item represents the deferred credit for an incentive or inducement received by a lessee from a lessor, in order to motivate the lessee to enter the lease agreement, which incentive or inducement is to be recognized as a reduction of rental expense over the lease term.

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The amount of revenue recognized for the period under subleasing arrangements.

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Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=ngvc_ChaletMember
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Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=ngvc_IselyFamilyLandTrustLLCMember
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