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Document And Entity Information (USD $)	12 Months Ended
Document And Entity Information (USD $)	Aug. 27, 2011	Feb. 25, 2011	Oct. 14, 2011 Common Class A [Member]	Oct. 14, 2011 Common Class B [Member]
Entity Information [Line Items]
Entity Registrant Name	UNIFIRST CORP
Entity Central Index Key	0000717954
Current Fiscal Year End Date	--08-27
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float		$ 801,785,035
Entity Common Stock, Shares Outstanding			14,989,871	4,885,277
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Aug. 27, 2011