Document And Entity Information (USD $)	12 Months Ended
	Aug. 25, 2012	Feb. 24, 2012	Oct. 12, 2012 Common Class A [Member]	Oct. 12, 2012 Common Class B [Member]
Entity Information [Line Items]
Entity Registrant Name	UNIFIRST CORP
Entity Central Index Key	0000717954
Current Fiscal Year End Date	--08-25
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float		$ 890,888,543
Entity Common Stock, Shares Outstanding			15,068,569	4,885,277
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Aug. 25, 2012