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

The fair value of the shares that, although not legally released, will be released by a future scheduled and committed debt service payment and will be allocated to employees for service rendered in the current accounting period and the shares contributed to the ESOP that have not yet been released, committed to be released, or allocated to participant accounts.

No definition available.

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

The shares that, although not legally released, will be released by a future scheduled and committed debt service payment and will be allocated to employees for service rendered in the current accounting period and shares contributed to the ESOP that have not yet been released, committed to be released, or allocated to participant accounts.

No definition available.

Name:	unfi_EmployeeStockOwnershipPlanESOPNumberOfCommittedToBeReleasedAndSuspenseShares
Namespace Prefix:	unfi_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Represents the number of shares issued to the employees under the ESOP, during the period.

No definition available.

Name:	unfi_EmployeeStockOwnershipPlanESOPNumberOfSharesDistributed
Namespace Prefix:	unfi_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Represents that number of shares or units in an ESOP trust that were released during the period to be assigned to individual participant accounts.

No definition available.

Name:	unfi_EmployeeStockOwnershipPlanESOPNumberOfSharesReleasedForAllocation
Namespace Prefix:	unfi_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Represents that number of shares or units in an ESOP trust that were allocated during the period to correct an operational error in prior years as elected in a Voluntary Correction Program filed with the IRS.

No definition available.

Name:	unfi_EmployeeStockOwnershipPlanESOPNumberOfSharesReleasedForAllocationCorrectAnOperationalErrorInPriorYears
Namespace Prefix:	unfi_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	unfi_EmployeeStockOwnershipPlanESOPSharesInESOPRollForward
Namespace Prefix:	unfi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the interest rate on a loan made to the ESOP by a lender other than the employer.

No definition available.

Name:	unfi_EmployeeStockOwnershipPlanInterestRateOnESOPDebt
Namespace Prefix:	unfi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the percentage of the entity's outstanding common stock repurchased and contributed to an employee stock ownership plan.

No definition available.

Name:	unfi_PercentageOfOutstandingCommonStockRepurchasedForEmployeeStockOwnershipPlan
Namespace Prefix:	unfi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the value of the entity's outstanding common stock repurchased and contributed to an employee stock ownership plan.

No definition available.

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

- Details

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

The shares or units in an ESOP trust that have been assigned to individual participant accounts based on a known formula. IRS rules require allocations to be nondiscriminatory generally based on compensation, length of service, or a combination of both. For any particular participant such shares or units may be vested, unvested, or partially vested.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

Name:	us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Sum of the allocated, committed-to-be-released and suspense shares of the entity held by the plan.

Name:	us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

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

For grandfathered ESOP shares acquired prior to January 1, 1993, the actual interest incurred on debt for obligations that the employer may secure on behalf of the ESOP.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 105

-SubTopic 10

-Section 70

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31814669&loc=SL6532572-165696

Name:	us-gaap_GrandfatheredESOPExpenseRecognitionActualInterestIncurredOnESOPDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

For grandfathered ESOP shares acquired prior to January 1, 1993, the amount of cash contributions made to the ESOP.