Employee Benefit Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Aug. 31, 2024	Aug. 26, 2023	Aug. 27, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions charged to expense under the plan	$ 20.3	$ 18.7	$ 18.2
SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amounts charged to expense related to the plan	1.7	1.7	1.5
Accumulated benefit obligations	23.4	22.5
UniFirst Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amounts charged to expense related to the plan	0.2	0.1	$ 0.1
Accumulated benefit obligations	3.6	3.5
Non-qualified Deferred Compensation Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amounts charged to expense related to the plan	0.8	0.3
NQDC Plan assets	3.3	2.0
NQDC Plan liabilities, current	$ 1.6	$ 0.5

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable within one year (or the operating cycle, if longer). Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

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Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
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Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
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Amount of cost for defined contribution plan.

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Amount of cost (reversal of cost) for pension benefits. Excludes other postretirement benefits.

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