Guarantor Obligations, Guarantees Term

No definition available.

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Namespace Prefix:	unfi_
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- Definition

Guarantor Obligations, Maximum Exposure, Discounted

+ References

No definition available.

+ Details

Name:	unfi_GuarantorObligationsMaximumExposureDiscounted
Namespace Prefix:	unfi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency, Insurance Coverage, Amount Above Deductible

+ References

No definition available.

+ Details

Name:	unfi_LossContingencyInsuranceCoverageAmountAboveDeductible
Namespace Prefix:	unfi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Loss Contingency, Insurance Deductible Amount

+ References

No definition available.

+ Details

Name:	unfi_LossContingencyInsuranceDeductibleAmount
Namespace Prefix:	unfi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Loss Contingency, Number Of Class Action Complaints

+ References

No definition available.

+ Details

Name:	unfi_LossContingencyNumberOfClassActionComplaints
Namespace Prefix:	unfi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Loss Contingency, Number Of Plaintiffs Dismissed

+ References

No definition available.

+ Details

Name:	unfi_LossContingencyNumberOfPlaintiffsDismissed
Namespace Prefix:	unfi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Professional Services Agreement, Base Amount

+ References

No definition available.

+ Details

Name:	unfi_ProfessionalServicesAgreementBaseAmount
Namespace Prefix:	unfi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Professional Services Agreement Term

+ References

No definition available.

+ Details

Name:	unfi_ProfessionalServicesAgreementTerm
Namespace Prefix:	unfi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_GuaranteeObligationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount awarded to other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

Name:	us-gaap_LitigationSettlementAmountAwardedToOtherParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of plaintiffs that have filed claims pertaining to a loss contingency.

+ References

No definition available.

+ Details

Name:	us-gaap_LossContingencyNumberOfPlaintiffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

Name:	us-gaap_PurchaseObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_PaymentGuaranteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationCaseAxis=unfi_MidwestPlaintiffsvs.SupervaluMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationStatusAxis=us-gaap_SettledLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=unfi_SUPERVALUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationCaseAxis=unfi_SupervaluInc.CustomerDataSecurityBreachLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=unfi_MoranFoodsLLCMember
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COMMITMENTS, CONTINGENCIES AND OFF-BALANCE SHEET ARRANGEMENTS (Details) $ in Millions			9 Months Ended
	Nov. 17, 2017 USD ($)	Aug. 30, 2017 plaintiff	Apr. 27, 2019 USD ($)	Nov. 30, 2014 complaint
Guarantor Obligations [Line Items]
Purchase Obligation			$ 0.3
Payment Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			41.9
Guarantor Obligations, Maximum Exposure, Discounted			$ 29.1
Minimum \| Payment Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Term			1 year
Maximum \| Payment Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Term			11 years
Weighted Average [Member] \| Payment Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Term			7 years
Midwest Plaintiffs vs. Supervalu [Member] \| Settled Litigation [Member] \| Supervalu
Guarantor Obligations [Line Items]
Litigation Settlement, Amount Awarded to Other Party	$ 9.0
Supervalu Inc. Customer Data Security Breach Litigation [Member] \| Supervalu
Guarantor Obligations [Line Items]
Loss Contingency, Number Of Class Action Complaints \| complaint				4
Loss Contingency, Number Of Plaintiffs Dismissed \| plaintiff		14
Loss Contingency, Number of Plaintiffs \| plaintiff		15
Loss Contingency, Insurance Coverage, Amount Above Deductible			$ 50.0
Loss Contingency, Insurance Deductible Amount			$ 1.0
Moran Foods, LLC [Member]
Guarantor Obligations [Line Items]
Professional Services Agreement Term			5 years
Professional Services Agreement, Base Amount			$ 30.0