Annual Melt Capacity

No definition available.

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Namespace Prefix:	cmc_
Data Type:	num:massItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Rebar Fabrication Facilities

+ References

No definition available.

+ Details

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Namespace Prefix:	cmc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the 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

+ Details

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

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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- Details

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- Details

Name:	us-gaap_BusinessAcquisitionAxis=cmc_U.S.RebarSteelMillandFabricationAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

Name:	us-gaap_DebtInstrumentAxis=cmc_CommitmentforSeniorSecuredTermLoanBFacilityMember
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SUBSEQUENT EVENTS (Details) t in Millions	Jan. 02, 2018 USD ($) fabrication_facility t	Nov. 30, 2017 USD ($)	Aug. 31, 2017 USD ($)
Subsequent Event
Subsequent Event [Line Items]
Annual melt capacity \| t	7.2
U.S. Rebar Steel Mill and Fabrication Assets \| Subsequent Event
Subsequent Event [Line Items]
Cash purchase price of acquisition	$ 600,000,000
Number of rebar fabrication facilities \| fabrication_facility	33
Annual melt capacity \| t	2.7
Revolving credit facility
Subsequent Event [Line Items]
Increase in credit facility for incremental term loans		$ 750,000,000
Term Loan \| Revolving credit facility
Subsequent Event [Line Items]
Increase in credit facility for incremental term loans		$ 150,000,000	$ 150,000,000
Term Loan \| Revolving credit facility \| Subsequent Event
Subsequent Event [Line Items]
Increase in credit facility for incremental term loans	$ 600,000,000
Commitment for Senior Secured Term Loan B Facility \| Term Loan \| Revolving credit facility \| Subsequent Event
Subsequent Event [Line Items]
Increase in credit facility for incremental term loans	$ 600,000,000