Document And Entity Information - USD ($)	12 Months Ended
	Sep. 01, 2018	Oct. 01, 2018	Mar. 03, 2018
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 01, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Registrant Name	MSC INDUSTRIAL DIRECT CO INC
Entity Central Index Key	0001003078
Current Fiscal Year End Date	--09-01
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Public Float			$ 3,957,389,283
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Trading Symbol	msm
Class A Common Stock [Member]
Entity Common Stock, Shares Outstanding		45,406,118
Class B Common Stock [Member]
Entity Common Stock, Shares Outstanding		10,369,547