Note 11 - Commitments and Contingencies (Details) - Changes to Environmental Liabilities - USD ($) $ in Thousands	12 Months Ended
Aug. 29, 2015	Aug. 30, 2014
Changes to Environmental Liabilities [Abstract]
Balance	$ 19,846	$ 19,680
Costs incurred for which reserves have been provided	(2,014)	(2,913)
Insurance proceeds	121	687
Interest accretion	603	716
Changes in discount rates	224	1,080
Revisions in estimates	4,527	596
Balance	$ 23,307	$ 19,846

No definition available.

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- Definition

Amount of discount applied to the future cost of environmental remediation to present value.

+ References

No definition available.

+ Details

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- Definition

Amount of interest accretion expense recognized during the period that is associated with environmental remediation costs. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Recorded amount of the individual components comprising the asset for insurance recoveries related to environmental remediation obligations.

+ References

No definition available.

+ Details

Name:	unf_RecordedInsuranceEnvironmentalRecoveriesAmount
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Data Type:	xbrli:monetaryItemType
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- Definition

Total costs accrued as of the balance sheet date for environmental loss contingencies.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 25

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The Increase or Decrease in the accrual for environmental loss in the period from revisions in estimates to existing obligations. The amount does not relate to changes in the environmental accrual related to business acquisitions or divestitures, or to currency movements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.Y.Q2)

-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

+ Details

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- Definition

The aggregate amount disbursed during the reporting period to settle environmental loss contingencies.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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