STOCKHOLDERS’ EQUITY AND EARNINGS PER SHARE ATTRIBUTABLE TO CMC (Calculations of the Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
May 31, 2016	May 31, 2015	May 31, 2016	May 31, 2015
Earnings Per Share [Abstract]
Earnings from continuing operations attributable to CMC	$ 35,111	$ 39,156	$ 71,593	$ 86,886
Basic earnings per share:
Shares outstanding for basic earnings per share (shares)	114,677,109	115,742,534	115,373,736	116,807,469
Basic earnings per share attributable to CMC: (in USD per share)	$ 0.31	$ 0.34	$ 0.62	$ 0.74
Diluted earnings per share:
Shares outstanding for basic earnings per share (shares)	114,677,109	115,742,534	115,373,736	116,807,469
Effect of dilutive securities:
Stock-based incentive/purchase plans (shares)	1,318,406	1,016,681	1,384,980	1,063,759
Shares outstanding for diluted earnings per share (shares)	115,995,515	116,759,215	116,758,716	117,871,228
Diluted earnings per share attributable to CMC: (in USD per share)	$ 0.30	$ 0.34	$ 0.61	$ 0.74
Anti-dilutive shares not included above (shares)	295,107	378,006	295,107	245,542

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Amount after tax of income (loss) from continuing operations attributable to the parent.

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