Consolidated Statements of Operations (USD $) In Thousands, except Per Share data	12 Months Ended
	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2009
Consolidated Statements of Operations [Abstract]
Net sales	$ 7,918,430	$ 6,306,102	$ 6,409,376
Costs and expenses:
Cost of goods sold	7,301,815	5,911,065	5,712,347
Selling, general and administrative expenses	537,113	520,369	612,563
Impairment of assets	118,795	3,766	5,568
Interest expense	70,806	75,508	76,964
Total costs and expenses	8,028,529	6,510,708	6,407,442
Earnings (loss) from continuing operations before taxes	(110,099)	(204,606)	1,934
Income taxes (benefit)	19,328	(38,118)	747
Earnings (loss) from continuing operations	(129,427)	(166,488)	1,187
Earnings (loss) from discontinued operations before taxes	(2,965)	(59,762)	31,991
Income taxes (benefit)	(2,988)	(21,142)	12,926
Earnings (loss) from discontinued operations	23	(38,620)	19,065
Net earnings (loss)	(129,404)	(205,108)	20,252
Less net earnings (loss) attributable to noncontrolling interests	213	236	(550)
Net earnings (loss) attributable to CMC	$ (129,617)	$ (205,344)	$ 20,802
Basic earnings (loss) per share attributable to CMC:
Earnings (loss) from continuing operations	$ (1.13)	$ (1.47)	$ 0.02
Earnings (loss) from discontinued operations		$ (0.34)	$ 0.17
Net earnings (loss)	$ (1.13)	$ (1.81)	$ 0.19
Diluted earnings (loss) per share attributable to CMC:
Earnings (loss) from continuing operations	$ (1.13)	$ (1.47)	$ 0.02
Earnings (loss) from discontinued operations		$ (0.34)	$ 0.16
Net earnings (loss)	$ (1.13)	$ (1.81)	$ 0.18