EARNINGS PER SHARE ATTRIBUTABLE TO CMC (Calculations of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Aug. 31, 2016	Aug. 31, 2015	Aug. 31, 2014
Earnings Per Share [Abstract]
Earnings from continuing operations	$ 72,543	$ 99,131	$ 117,606
Basic earnings per share:
Shares outstanding for basic earnings per share	115,211,490	116,527,265	117,496,270
Basic earnings per share from continuing operations attributable to CMC (USD per share)	$ 0.63	$ 0.85	$ 1.00
Diluted earnings per share:
Shares outstanding for basic earnings per share	115,211,490	116,527,265	117,496,270
Effect of dilutive securities:
Stock-based incentive/purchase plans	1,412,336	1,422,633	1,110,836
Shares outstanding for diluted earnings per share	116,623,826	117,949,898	118,607,106
Diluted earnings per share from continuing operations attributable to CMC (USD per share)	$ 0.62	$ 0.84	$ 0.99
Anti-dilutive shares not included above	274,251	371,273	679,916

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 including portion attributable to the noncontrolling interest.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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