QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Aug. 31, 2014		May 31, 2014		Feb. 28, 2014		Nov. 30, 2013		Aug. 31, 2013		May 31, 2013		Feb. 28, 2013		Nov. 30, 2012		Aug. 31, 2014	Aug. 31, 2013	Aug. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 1,903,196	[1]	$ 1,804,774	[1]	$ 1,649,098	[1]	$ 1,682,891	[1]	$ 1,698,861	[1]	$ 1,752,534	[1]	$ 1,688,665	[1]	$ 1,749,515	[1]	$ 7,039,959	$ 6,889,575	$ 7,656,375
Gross profit	186,078	[1]	183,298	[1]	145,190	[1]	181,093	[1]	160,788	[1]	175,519	[1]	139,365	[1]	186,665	[1]
Net earnings attributable to CMC	$ 34,926		$ 23,563		$ 11,143		$ 45,919		$ 4,057		$ 18,964		$ 4,577		$ 49,717		$ 115,551	$ 77,315	$ 207,484
Basic EPS attributable to CMC	$ 0.29		$ 0.20		$ 0.09		$ 0.39		$ 0.03		$ 0.16		$ 0.04		$ 0.43		$ 0.98	$ 0.66	$ 1.79
Diluted EPS attributable to CMC	$ 0.29		$ 0.20		$ 0.09		$ 0.39		$ 0.03		$ 0.16		$ 0.04		$ 0.42		$ 0.97	$ 0.66	$ 1.78

[1] Excludes divisions classified as discontinued operations. See Note 10, Businesses Held for Sale, Discontinued Operations and Dispositions.