Leases, Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
Aug. 31, 2025	Aug. 31, 2024	Aug. 31, 2023
Leases [Abstract]
Operating lease expense	$ 48,618	$ 46,515	$ 40,093
Finance lease expense:
Amortization of assets	27,966	23,825	16,574
Interest on lease liabilities	7,690	5,712	3,642
Total finance lease expense	35,656	29,537	20,216
Variable and short-term lease expense	20,901	19,481	20,810
Total lease expense	$ 105,175	$ 95,533	$ 81,119

Finance Lease, Cost

No definition available.

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Balance Type:	debit
Period Type:	duration

- Definition

Variable and Short-term Lease cost

+ References

No definition available.

+ Details

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

- Definition

Amount of interest expense on finance lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 53
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479589/842-20-55-53

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-4

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-4

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of amortization expense attributable to right-of-use asset from finance lease.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of lease cost recognized by lessee for lease contract.

+ References

+ Details

Name:	us-gaap_LeaseCost
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Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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- References

No definition available.

+ Details

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- Definition

Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

+ References

+ Details

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Balance Type:	debit
Period Type:	duration