Employee Benefit Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 26, 2023	Aug. 27, 2022	Aug. 28, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions charged to expense under the plan	$ 18.7	$ 18.2	$ 19.9
SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amounts charged to expense related to the plan	1.7	1.5	2.9
Accumulated benefit obligations	22.5	24.6
UniFirst Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amounts charged to expense related to the plan	0.1	0.1	$ 0.2
Accumulated benefit obligations	3.5	3.8
Nonqualified Deferred Compensation Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amounts charged to expense related to the plan	0.3	0.3
NQDC Plan assets	$ 2.0	$ 1.3