Represents the numerator of the minimum fixed charge coverage ratio allowable under the financial covenant.

No definition available.

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Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of rolling quarters used to calculate the fixed charge coverage ratio under the debt instrument covenants.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
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- Definition

The initial applicable margin percentage points added to the debt instrument.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the amount of reserves that reduce the available borrowing capacity under the existing revolving credit facility on a dollar for dollar basis.

+ References

No definition available.

+ Details

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

- Definition

The maximum amount of borrowing capacity under a line of credit that is used for calculating to minimum fixed charge ration.

+ References

No definition available.

+ Details

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

- Definition

The percentage of maximum amount of borrowing capacity under a line of credit that is used for calculating to minimum fixed charge ration.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of the average daily balance of amounts actually used (other than swingline loans) line of credit facility, under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	unfi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Details

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- Details

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- Details

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- Details

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Balance Type:
Period Type:

- Details

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

- Details

Name:	unfi_DebtInstrumentVariableRateBaseAxis=unfi_DebtInstrumentVariableRateFederalFundsEffectiveRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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NOTES PAYABLE (Details)	Aug. 31, 2018 USD ($)	Apr. 29, 2016 USD ($) quarter	May 31, 2012	Aug. 30, 2018 USD ($)	Jul. 28, 2018 USD ($)	May 28, 2014 USD ($)
Notes payable
Line of Credit Facility, Commitment Fee Percentage		0.125%
Letter of credit commitments					$ 24,300,000
Minimum
Notes payable
Maximum borrowing base		$ 10,000,000		$ 10,000,000
Amended and restated revolving credit facility
Notes payable
Maximum borrowing base		850,000,000.0		1,950,000,000.0
Additional increase in borrowing base	$ 600,000,000.0	$ 600,000,000
Borrowing base, based on eligible accounts receivable and inventory levels					884,500,000
Amount outstanding					210,000,000
Letter of credit commitments					24,300,000
Reserves					4,200,000
Remaining availability of credit facility					$ 650,200,000
Minimum fixed charge coverage ratio, numerator		1.0
Number of quarters used to calculate fixed charge coverage ratio \| quarter		4
Percentage of maximum aggregate availability of the aggregate borrowing base (as a percent)		10.00%
Amended and restated revolving credit facility \| Minimum
Notes payable
Line of Credit Facility, Maximum Aggregate Availability of the Aggregate Borrowing Base						$ 60,000,000.0
Amended and restated revolving credit facility \| U.S. Borrowers
Notes payable
Spread on reference rate (as a percent)		0.25%
Amended and restated revolving credit facility \| UNFI Canada
Notes payable
Maximum borrowing base		$ 50,000,000.0		$ 50,000,000.0
Spread on reference rate (as a percent)		0.25%
Amended and restated revolving credit facility \| UNFI Canada \| Minimum
Notes payable
Annual commitment fee, percentage (as a percent)		0.25%
Amended and restated revolving credit facility \| UNFI Canada \| Maximum
Notes payable
Annual commitment fee, percentage (as a percent)		0.30%
Average daily balance of amounts actually used for annual commitments fee, percentage (as a percent)		25.00%
Amended and restated revolving credit facility \| Federal funds effective rate \| U.S. Borrowers
Notes payable
Reference rate		federal funds effective rate
Spread on reference rate (as a percent)		0.50%
Amended and restated revolving credit facility \| One-month LIBOR \| U.S. Borrowers
Notes payable
Reference rate		LIBOR
Spread on reference rate (as a percent)		1.00%
Amended and restated revolving credit facility \| LIBOR \| U.S. Borrowers
Notes payable
Initial applicable margin						1.25%
Amended and restated revolving credit facility \| Nine month LIBOR \| U.S. Borrowers
Notes payable
Reference rate			nine months LIBOR
Amended and restated revolving credit facility \| Reuters Canadian Deposit Offering Rate \| UNFI Canada
Notes payable
Reference rate		30-day Reuters Canadian Deposit Offering Rate ("CDOR")
Spread on reference rate (as a percent)		0.50%
Amended and restated revolving credit facility \| Prime rate of Bank of America N.A.'s Canada branch \| UNFI Canada
Notes payable
Reference rate			Bankers' acceptance equivalent rate for a one month interest period
Spread on reference rate (as a percent)		1.00%
Amended and restated revolving credit facility \| Annual rates applicable to Canadian Dollar bankers' acceptances \| UNFI Canada
Notes payable
Reference rate			annual rates applicable to CanadianDollar bankers' acceptances
Spread on reference rate (as a percent)			0.05%