Debt And Capital Lease Obligations (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
May 26, 2012	Jun. 30, 2011
Debt Instrument [Line Items]
Unsecured credit facility		$ 200,000
Available increase in amount borrowed		250,000
Incremental payment of additional borrowings		50,000
Maturity date	Jun. 08, 2016
Borrowing rate under Credit Facility	1.24%
Quarterly fronting fee	0.125%
Capital leases and financing obligations for certain information technology equipment entered into	4,440
Amount due under all capital leases and financing agreements	3,719
Current maturities of capital lease and financing obligations	1,417
Property and equipment acquired under capital leases and financing agreements	$ 3,912
LIBOR [Member]
Debt Instrument [Line Items]
Percentage points in addition to reference rate used in computation of variable rate on debt instrument	1.00%
Federal Funds Effective Rate Plus [Member]
Debt Instrument [Line Items]
Percentage points in addition to reference rate used in computation of variable rate on debt instrument	0.50%
One-Month Interest Period [Member] \| LIBOR Interest Period Plus [Member]
Debt Instrument [Line Items]
Percentage points in addition to reference rate used in computation of variable rate on debt instrument	1.00%
Minimum [Member]
Debt Instrument [Line Items]
Percentage points in addition to reference rate used in computation of variable rate on debt instrument	0.00%
Quarterly undrawn fee	0.15%
Quarterly letter of credit usage fees	1.00%
Minimum [Member] \| Alternate Base Rate [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Percentage points in addition to reference rate used in computation of variable rate on debt instrument	1.00%
Maximum [Member]
Debt Instrument [Line Items]
Percentage points in addition to reference rate used in computation of variable rate on debt instrument	0.25%
Quarterly undrawn fee	0.20%
Quarterly letter of credit usage fees	1.25%
Maximum [Member] \| Alternate Base Rate [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Percentage points in addition to reference rate used in computation of variable rate on debt instrument	1.25%

Available increase in aggregate amount borrowed

No definition available.

Name:	msm_AvailableIncreaseInAggregateAmountBorrowed
Namespace Prefix:	msm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Increase increments in amount borrowed

+ References

No definition available.

+ Details

Name:	msm_IncreaseIncrementsInAmountBorrowed
Namespace Prefix:	msm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fronting fee is the administrative fee paid to the lead credit issuer.

+ References

No definition available.

+ Details

Name:	msm_QuarterlyFrontingFee
Namespace Prefix:	msm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Quarterly letter of credit usage fees

+ References

No definition available.

+ Details

Name:	msm_QuarterlyLetterOfCreditUsageFees
Namespace Prefix:	msm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

+ Details

Name:	us-gaap_CapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The increase during the period in capital lease obligations due to entering into new capital leases.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 32

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_CapitalLeaseObligationsIncurred
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The total gross amount less the charge for the use of the long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

+ Details

Name:	us-gaap_CapitalLeasesBalanceSheetAssetsByMajorClassNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Obligation related to long-term debt (excluding convertible debt) and capital leases, the portion which is due in one year or less in the future.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant