Name:	unf_AccretionOnEnvironmentalContingencies
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

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

No definition available.

Name:	unf_EnvironmentalLiabilitiesChangesInDiscountRates
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

No definition available.

Name:	unf_RecordedInsuranceEnvironmentalRecoveriesAmount
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

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

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=82911808&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

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Amount of expense (reversal of expense) which increases (decreases) the accrual for environmental loss contingencies from revisions in estimates to existing obligations. Excludes changes related to business acquisitions, divestitures, or currency movement.

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

Name:	us-gaap_AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates
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Amount of cash outflow to settle environmental loss contingencies.

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.