Transfer of Accounts Receivable Program, Face Amount

No definition available.

Name:	cmc_TransferofAccountsReceivableProgramFaceAmount
Namespace Prefix:	cmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Transfers of Accounts Receivable Outstanding

+ References

No definition available.

+ Details

Name:	cmc_TransfersofAccountsReceivableOutstanding
Namespace Prefix:	cmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- 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://fasb.org/us-gaap/role/ref/legacyRef
-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

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

- Definition

Fair value of the amount outstanding under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

+ Details

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

- Details

Name:	dei_LegalEntityAxis=cmc_CmcpMember
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

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

- Details

Name:	us-gaap_DebtInstrumentAxis=cmc_U.S.ProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cmc_PolandProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

CREDIT ARRANGEMENTS (Narrative) (Details)	May 31, 2020 PLN (zł)	May 31, 2020 USD ($)	Aug. 31, 2019 USD ($)
CMCP
Debt Instrument [Line Items]
Revolving credit facility current borrowing capacity	zł 275,000,000.0	$ 68,600,000
Revolving credit facility, amount drawn		22,400,000	$ 0
Stand by letters of credit outstanding amount		800,000	1,100,000
Revolving credit facility
Debt Instrument [Line Items]
Revolving credit facility current borrowing capacity		350,000,000.0	350,000,000.0
Revolving credit facility, amount drawn		0	0
Stand-by letters of credit
Debt Instrument [Line Items]
Stand by letters of credit outstanding amount		3,000,000.0	3,000,000.0
U.S. Program
Debt Instrument [Line Items]
Advances outstanding under transfer of receivables programs		0	0
Poland Program
Debt Instrument [Line Items]
Transfer of accounts receivable program limit	zł 220,000,000.0	54,900,000
Advances outstanding under transfer of receivables programs		$ 2,800,000	$ 3,900,000