Name:	unf_AccrualForEnvironmentalLossContingenciesEffectOfInflation
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Accrual for environmental loss contingencies, net of estimated insurance proceeds, total.

No definition available.

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Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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The portion of the estimated aggregate undiscounted amount of the accrual for environmental loss contingencies that is expected to be paid, net of estimated insurance proceeds expected to be received, after the fifth year of the balance sheet date.

No definition available.

Name:	unf_AccrualForEnvironmentalLossContingenciesUndiscountedDueAfterFifthYearNetOfEstimatedInsuranceProceeds
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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No definition available.

Name:	unf_AccrualForEnvironmentalLossContingenciesUndiscountedDueInFiveYearsNetOfEstimatedInsuranceProceeds
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

No definition available.

Name:	unf_AccrualForEnvironmentalLossContingenciesUndiscountedDueInFourYearsNetOfEstimatedInsuranceProceeds
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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No definition available.

Name:	unf_AccrualForEnvironmentalLossContingenciesUndiscountedDueInThreeYearsNetOfEstimatedInsuranceProceeds
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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No definition available.

Name:	unf_AccrualForEnvironmentalLossContingenciesUndiscountedDueInTwoYearsNetOfEstimatedInsuranceProceeds
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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No definition available.

Name:	unf_AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYearNetOfEstimatedInsuranceProceeds
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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Accrual for Environmental Loss Contingencies, Net of Estimated Insurance Proceeds, Fiscal Year Maturity [Abstract]

No definition available.

Name:	unf_AccrualforEnvironmentalLossContingenciesNetofEstimatedInsuranceProceedsFiscalYearMaturityAbstract
Namespace Prefix:	unf_
Data Type:	xbrli:stringItemType
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The estimated aggregate undiscounted amount of the estimated insurance proceeds accrual for environmental loss contingencies as of the balance sheet date.

No definition available.

Name:	unf_EstimatedInsuranceProceedsForEnvironmentalLossContingenciesGross
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The portion of the estimated aggregate undiscounted amount of the insurance proceeds for environmental loss contingencies that is expected to be received after the fifth year of the balance sheet date.

No definition available.

Name:	unf_EstimatedInsuranceProceedsForEnvironmentalLossContingenciesUndiscountedDueAfterFifthYear
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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The portion of the estimated aggregate undiscounted amount of the insurance proceeds for environmental loss contingencies that is expected to be received within five years of the balance sheet date.

No definition available.

Name:	unf_EstimatedInsuranceProceedsForEnvironmentalLossContingenciesUndiscountedDueInFifthYear
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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The portion of the estimated aggregate undiscounted amount of the insurance proceeds for environmental loss contingencies that is expected to be received within four years of the balance sheet date.

No definition available.

Name:	unf_EstimatedInsuranceProceedsForEnvironmentalLossContingenciesUndiscountedDueInFourthYear
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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The portion of the estimated aggregate undiscounted amount of the insurance proceeds for environmental loss contingencies that is expected to be received within two years of the balance sheet date.

No definition available.

Name:	unf_EstimatedInsuranceProceedsForEnvironmentalLossContingenciesUndiscountedDueInSecondYear
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The portion of the estimated aggregate undiscounted amount of the insurance proceeds for environmental loss contingencies that is expected to be received within three years of the balance sheet date.

No definition available.

Name:	unf_EstimatedInsuranceProceedsForEnvironmentalLossContingenciesUndiscountedDueInThirdYear
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The portion of the estimated aggregate undiscounted amount of the insurance proceeds for environmental loss contingencies that is expected to be received within one year of the balance sheet date.

No definition available.

Name:	unf_EstimatedInsuranceProceedsForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear
Namespace Prefix:	unf_
Data Type:	xbrli:monetaryItemType
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Estimated Insurance Proceeds for Environmental Loss Coontingencies, Fiscal Year Maturity [Abstract]

No definition available.

Name:	unf_EstimatedInsuranceProceedsforEnvironmentalLossCoontingenciesFiscalYearMaturityAbstract
Namespace Prefix:	unf_
Data Type:	xbrli:stringItemType
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Total costs accrued as of the balance sheet date for environmental loss contingencies.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-1

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481931/410-30-50-10

Reference 3: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (d)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481931/410-30-50-10

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 16
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481899/410-30-55-16

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.Y.Q1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480102/450-20-S99-1

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481931/410-30-50-7

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Amount of imputed interest necessary to reduce (reconcile) the undiscounted amount of the accrual for environmental loss contingencies to the present value.

Name:	us-gaap_AccrualForEnvironmentalLossContingenciesDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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- References

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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Undiscounted amount of the accrual for environmental loss contingencies.

Name:	us-gaap_AccrualForEnvironmentalLossContingenciesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Undiscounted amount of accrual for environmental loss contingency to be paid after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.Y.Q1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480102/450-20-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 410
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481931/410-30-50-7

Name:	us-gaap_AccrualForEnvironmentalLossContingenciesUndiscountedDueAfterFifthYear
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Undiscounted amount of accrual for environmental loss contingency to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Namespace Prefix:	us-gaap_
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Undiscounted amount of accrual for environmental loss contingency to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Namespace Prefix:	us-gaap_
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Undiscounted amount of accrual for environmental loss contingency to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Undiscounted amount of accrual for environmental loss contingency to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Namespace Prefix:	us-gaap_
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Undiscounted amount of accrual for environmental loss contingency to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).