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Asset Retirement Obligations - Narrative (Details) | 12 Months Ended
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Aug. 25, 2018
Asset Retirement Obligations [Line Items] |
Estimated impact of inflation per year | 3.00%
Credit-adjusted risk-free rates, minimum | 7.00%
Credit-adjusted risk-free rates, maximum | 7.50%
Minimum |
Asset Retirement Obligations [Line Items] |
Remaining lives | 2 years
Maximum |
Asset Retirement Obligations [Line Items] |
Remaining lives | 26 years

X
- Definition This element describes the minimum years the Company will discount the liability of estimated future costs to decommission one of its facilities. + References No definition available. + Details
Name: | unf_AssetRetirementObligationRemainingLives
Namespace Prefix: | unf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition [Line Items] for Asset Retirement Obligations [Table] + References No definition available. + Details
Name: | unf_AssetRetirementObligationsLineItems
Namespace Prefix: | unf_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition This element represents the maximum rate that a liability is discounted, using a credit-adjusted risk-free rate. Credit-adjusting the risk-free rate means adding to the Treasury rates some amount of additional interest-rate basis points to reflect the fact that companies might default on their debt obligations. + References No definition available. + Details
Name: | unf_CreditAdjustedRiskFreeRatesMaximumRate
Namespace Prefix: | unf_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition This element represents the minimum rate that a liability is discounted, using a credit-adjusted risk-free rate. Credit-adjusting the risk-free rate means adding to the Treasury rates some amount of additional interest-rate basis points to reflect the fact that companies might default on their debt obligations. + References No definition available. + Details
Name: | unf_CreditAdjustedRiskFreeRatesMinimumRate
Namespace Prefix: | unf_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition This element represents the percentage added to estimated current cost of decommissioning one of the Company's facilities based on future estimated inflation rate. + References No definition available. + Details
Name: | unf_EstimatedImpactOfInflationPerYear
Namespace Prefix: | unf_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |