Document and Entity Information (USD $)
 9 Months Ended
May 31, 2011
Jul. 01, 2011
Feb. 26, 2010
Document and Entity Information [Abstract]      
Entity Registrant Name COMMERCIAL METALS CO    
Entity Central Index Key 0000022444    
Document Type 10-Q    
Document Period End Date May 31, 2011
Amendment Flag false    
Document Fiscal Year Focus 2011    
Document Fiscal Period Focus Q3    
Current Fiscal Year End Date --08-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 1,612,607,063
Entity Common Stock, Shares Outstanding   115,533,540 Â