STOCKHOLDERS’ EQUITY AND EARNINGS PER SHARE ATTRIBUTABLE TO CMC (Narrative) (Details) (USD $)	3 Months Ended	6 Months Ended
	Feb. 28, 2015	Feb. 28, 2015	Oct. 27, 2014
Earnings Per Share [Abstract]
Stock repurchase program, authorized amount			$ 100,000,000.0
Stock repurchase program, shares purchased (shares)	2,202,342	2,762,835
Stock repurchase program, average purchase price per share (in USD per share)	$ 13.73	$ 14.33
Stock repurchase program, remaining authorized repurchase amount	$ 60,400,000	$ 60,400,000