Cover Page - shares	6 Months Ended
	Feb. 28, 2021	Mar. 23, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Feb. 28, 2021
Document Transition Report	false
Entity File Number	1-4304
Entity Registrant Name	COMMERCIAL METALS COMPANY
Entity Incorporation, State or Country Code	DE
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
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	CMC
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		120,510,370
Entity Central Index Key	0000022444
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--08-31