SIGNIFICANT ACCOUNTING POLICIES (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Oct. 27, 2012	Aug. 02, 2014	Aug. 03, 2013	Jul. 28, 2012
Goodwill
Percentage for qualitative assessment (as a percent)		20.00%
Minimum pre-tax operating income threshold as a percentage of prior year amounts for goodwill allocation		85.00%
Percentage of maximum net income decreased (as a percent)		15.00%
Impairment of indefinite lived intangibles	$ 1,600	$ 0	$ 1,629	$ 0
Changes in the carrying amount of goodwill and the amount allocated by reportable segment
Balance at beginning of period	193,741us-gaap_Goodwill	201,874us-gaap_Goodwill	193,741us-gaap_Goodwill
Goodwill adjustment for prior year business combinations			8,979
Goodwill from current year business combinations		73,966us-gaap_GoodwillAcquiredDuringPeriod
Contingent consideration for prior year business combinations		62	200
Change in foreign exchange rates		(1,354)us-gaap_GoodwillTranslationAdjustments	(1,046)us-gaap_GoodwillTranslationAdjustments
Balance at end of period		274,548us-gaap_Goodwill	201,874us-gaap_Goodwill	193,741us-gaap_Goodwill
Wholesale
Goodwill
Allocated percentage of goodwill		93.50%
Changes in the carrying amount of goodwill and the amount allocated by reportable segment
Balance at beginning of period	176,210	184,143	176,210
Goodwill adjustment for prior year business combinations			8,979
Goodwill from current year business combinations		73,966	8,979
Contingent consideration for prior year business combinations		62	0
Change in foreign exchange rates		(1,354)	(1,046)
Balance at end of period		256,817	184,143
Other
Changes in the carrying amount of goodwill and the amount allocated by reportable segment
Balance at beginning of period	17,531	17,731	17,531
Goodwill adjustment for prior year business combinations			0
Goodwill from current year business combinations		0
Contingent consideration for prior year business combinations		0	200
Change in foreign exchange rates		0	0
Balance at end of period		$ 17,731	$ 17,731

Business Acquisition, Contingent Consideration for Prior Year Business Combinations

No definition available.

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

- Definition

Represents the threshold percentage for qualitative assessment determination used in fiscal 2012 was for any reporting units that exceeded the first step in the prior year test.

+ References

No definition available.

+ Details

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

- Definition

Represents the percentage of goodwill allocation within the entity's segments.

+ References

No definition available.

+ Details

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

- Definition

Reporting Unit, Minimum Pre-tax Operating Income Threshold as a Percentage of Prior Year Amounts for Goodwill Allocation

+ References

No definition available.

+ Details

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

- Definition

Represents the maximum percentage of net income decreased for each reporting unit.

+ References

No definition available.

+ Details

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

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

+ Details

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

- Details

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

- Definition

Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 16

-URI http://asc.fasb.org/extlink&oid=21917927&loc=d3e961-128460

+ Details

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

- Details

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

- Definition

Amount of increase (decrease) from foreign currency translation adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

+ Details

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

- Definition

Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16373-109275

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_AllOtherSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: