This represents disposal price of a business unit or asset during divestiture.

No definition available.

Name:	cmc_BusinessDivestitureDisposalPrice
Namespace Prefix:	cmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

It represents escrow receivable related to business or asset disposal.

+ References

No definition available.

+ Details

Name:	cmc_Escrowreceivable
Namespace Prefix:	cmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

For investments in debt and equity securities accounted for at cost, the excess of net sale proceeds over the carrying amount of investments disposed of during the period.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph c, d

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.7(c))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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

- Definition

Amount of gain (loss), before tax expense or benefit and not previously recognized, resulting from the sale of a business component.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e957-107759

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

+ Details

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

- Details

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

- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company before stock transaction.

+ References

No definition available.

+ Details

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

Businesses Held For Sale, Discontinued Operations And Dispositions (Narrative) (Details) (USD $)	3 Months Ended			0 Months Ended	3 Months Ended
	Nov. 30, 2013	Nov. 30, 2012	Nov. 30, 2012 CMCS [Member]	Oct. 17, 2013 Howell [Member]	Nov. 30, 2013 Howell [Member]	Nov. 30, 2012 Trinecke Zelezarny [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business divestiture disposal price			$ 3,900,000	$ 58,500,000		$ 29,000,000
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax					23,800,000
Escrow receivable				4,200,000
Sale of Stock, Percentage of Ownership before Transaction						11.00%
Cost-method investments, pre-tax gains	$ 0	$ 26,088,000				$ 26,100,000