Document And Entity Information - USD ($)	12 Months Ended
	Aug. 29, 2015	Oct. 16, 2015	Feb. 27, 2015
Document Information [Line Items]
Entity Registrant Name	UNIFIRST CORP
Trading Symbol	unf
Document Type	10-K
Current Fiscal Year End Date	--08-29
Entity Public Float			$ 1,773,089,167
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. 29, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		4,854,519
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		15,254,424