STOCKHOLDERS’ EQUITY AND EARNINGS PER SHARE ATTRIBUTABLE TO CMC (Calculations of the Basic and Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
Nov. 30, 2014	Nov. 30, 2013
Earnings Per Share [Abstract]
Earnings from continuing operations	$ 38,334	$ 33,700
Basic earnings per share:
Shares outstanding for basic earnings per share	117,818,170	117,070,499
Basic earnings per share attributable to CMC:	$ 0.33	$ 0.29
Diluted earnings per share:
Shares outstanding for basic earnings per share	117,818,170	117,070,499
Effect of dilutive securities:
Stock-based incentive/purchase plans	1,091,448	1,086,112
Shares outstanding for diluted earnings per share	118,909,618	118,156,611
Diluted earnings per share attributable to CMC:	$ 0.32	$ 0.29
Anti-dilutive shares not included above	672,352	1,364,036

STOCKHOLDERS’ EQUITY AND EARNINGS PER SHARE ATTRIBUTABLE TO CMC (Calculations of the Basic and Diluted Earnings Per Share) (Details) (USD $)
In Thousands, except Share data, unless otherwise specified

3 Months Ended

Nov. 30, 2014

Nov. 30, 2013

Earnings Per Share [Abstract]

Earnings from continuing operations

$ 38,334us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest

$ 33,700us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest

Basic earnings per share:

Shares outstanding for basic earnings per share

117,818,170us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

117,070,499us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

Basic earnings per share attributable to CMC:

$ 0.33us-gaap_IncomeLossFromContinuingOperationsPerBasicShare

$ 0.29us-gaap_IncomeLossFromContinuingOperationsPerBasicShare

Diluted earnings per share:

Shares outstanding for basic earnings per share

117,818,170us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

117,070,499us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

Effect of dilutive securities:

Stock-based incentive/purchase plans

1,091,448us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

1,086,112us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

Shares outstanding for diluted earnings per share

118,909,618us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

118,156,611us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

Diluted earnings per share attributable to CMC:

$ 0.32us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare

$ 0.29us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare

Anti-dilutive shares not included above

672,352us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

1,364,036us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses and taxes from ongoing operations before extraordinary items, and 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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