Consolidated Statements of Operations (Unaudited) (USD $)
In Thousands, except Share data
 3 Months Ended 9 Months Ended
May 31, 2011
May 31, 2010
May 31, 2011
May 31, 2010
Consolidated Statements of Operations [Abstract]        
Net sales $ 2,076,564 $ 1,765,154 $ 5,650,810 $ 4,489,855
Costs and expenses:        
Cost of goods sold 1,861,125 1,645,250 5,205,197 4,253,574
Selling, general and administrative expenses 145,597 108,509 390,772 389,182
Interest expense 18,254 18,184 54,857 57,871
Total cost and expense 2,024,976 1,771,943 5,650,826 4,700,627
Earnings (loss) from continuing operations before income taxes 51,588 (6,789) (16) (210,772)
Income taxes (benefit) 14,493 3,952 8,688 (36,101)
Earnings (loss) from continuing operations 37,095 (10,741) (8,704) (174,671)
Earnings (loss) from discontinued operations before taxes (1,429) 4,001 (782) (62,513)
Income taxes (benefit) (554) 1,723 (303) (24,117)
Earnings (loss) from discontinued operations (875) 2,278 (479) (38,396)
Net earnings (loss) 36,220 (8,463) (9,183) (213,067)
Less net earnings attributable to noncontrolling interests 55 363 163 278
Net earnings loss attributable to CMC $ 36,165 $ (8,826) $ (9,346) $ (213,345)
Basic earnings (loss) per share attributable to CMC:        
Earnings (loss) from continuing operations $ 0.32 $ (0.1) $ (0.08) $ (1.54)
Earnings (loss) from discontinued operations $ (0.01) $ 0.02   $ (0.34)
Net earnings (loss) $ 0.31 $ (0.08) $ (0.08) $ (1.88)
Diluted earnings (loss) per share attributable to CMC:        
Earnings (loss) from continuing operations $ 0.32 $ (0.1) $ (0.08) $ (1.54)
Earnings (loss) from discontinued operations $ (0.01) $ 0.02   $ (0.34)
Net earnings (loss) $ 0.31 $ (0.08) $ (0.08) $ (1.88)
Cash dividends per share $ 0.12 $ 0.12 $ 0.36 $ 0.36
Average basic shares outstanding 115,403,374 114,067,149 114,819,792 113,279,301
Average diluted shares outstanding 116,360,755 114,067,149 114,819,792 113,279,301