Document And Entity Information (USD $)	12 Months Ended
	Aug. 30, 2014	Feb. 28, 2014	Oct. 17, 2014 Common Class A [Member]	Oct. 17, 2014 Common Class B [Member]
Document Information [Line Items]
Entity Registrant Name	UNIFIRST CORP
Document Type	10-K
Current Fiscal Year End Date	--08-30
Entity Common Stock, Shares Outstanding			15,193,047	4,860,519
Entity Public Float		$ 1,622,023,215
Amendment Flag	false
Entity Central Index Key	0000717954
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Document Period End Date	Aug. 30, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY