| Cover | Oct. 13, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 13, 2021 |
| Entity Registrant Name | Commercial Metals Company |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-4304 |
| Entity Tax Identification Number | 75-0725338 |
| Entity Address, Address Line One | 6565 N. MacArthur Blvd. |
| Entity Address, City or Town | Irving |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 75039 |
| City Area Code | 214 |
| Local Phone Number | 689-4300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Trading Symbol | CMC |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000022444 |
| Amendment Flag | false |
