Accounting Policies (Policies)	9 Months Ended
Accounting Policies (Policies)	May 31, 2013
Accounting Policies [Abstract]
Accounting principles	Accounting Principles The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP") on a basis consistent with that used in the Annual Report on Form 10-K filed by Commercial Metals Company ("CMC," and together with its consolidated subsidiaries, the "Company") with the Securities and Exchange Commission ("SEC") for the year ended August 31, 2012, and include all normal recurring adjustments necessary to present fairly the consolidated balance sheets, statements of operations, comprehensive income (loss), cash flows and stockholders' equity for the periods indicated. Certain amounts in fiscal 2012 have been reclassified to conform to the fiscal 2013 presentation. These notes should be read in conjunction with the audited consolidated financial statements and notes included in the Annual Report on Form 10-K for the year ended August 31, 2012. The results of operations for the three and nine month periods are not necessarily indicative of the results to be expected for the full year.
Recent accounting pronouncements	Recent Accounting Pronouncements In the first quarter of 2013, the Company adopted guidance issued by the Financial Accounting Standards Board ("FASB") on disclosure requirements for the presentation of comprehensive income (loss). This guidance requires entities to report components of comprehensive income (loss) in either (1) a continuous statement of comprehensive income (loss) or (2) two separate but consecutive statements. As a result of the adoption, the Company's financial statements now include a separate consolidated statement of comprehensive income (loss) immediately following the consolidated statements of operations. In the first quarter of 2013, the Company adopted guidance that simplifies how entities test indefinite-lived intangible assets for impairment and improves consistency in impairment testing guidance among long-lived asset categories. The guidance permits entities to first assess qualitative factors to determine whether it is more likely than not that an indefinite-lived intangible asset is impaired as a basis for determining whether it is necessary to perform the quantitative impairment test in accordance with U.S. generally accepted accounting principles. An entity will have an option not to calculate annually the fair value of an indefinite-lived intangible asset if the entity determines that it is not more likely than not that the asset is impaired. The adoption of this guidance did not have a material impact on the Company's consolidated financial statements. In April 2013, the FASB issued guidance requiring an entity to prepare its financial statements using the liquidation basis of accounting when liquidation is imminent. In addition, the guidance provides principles for the recognition and measurement of assets and liabilities and requirements for financial statements prepared using the liquidation basis of accounting. The new guidance is effective prospectively for entities that determine liquidation is imminent during fiscal years, and interim reporting periods within those years, beginning after December 15, 2013. The Company does not expect this guidance to have a material impact on its consolidated financial statements. In March 2013, the FASB issued guidance requiring an entity to release any related cumulative translation adjustment into net income when it either sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets that is a nonprofit activity or a business within a foreign entity. In addition, the guidance resolves the diversity in practice for the treatment of business combinations achieved in stages involving a foreign entity. The new guidance is effective prospectively for fiscal years, and interim reporting periods within those years, beginning after December 15, 2013. The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements. In February 2013, the FASB issued guidance requiring an entity to disclose additional information about reclassifications out of accumulated other comprehensive income (loss), including (1) changes in accumulated other comprehensive income (loss) balances by component and (2) significant items reclassified out of accumulated other comprehensive income (loss) and the effect on the respective line items in net income if the amounts are required to be reclassified in their entirety to net income. For other amounts that are not required to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference to other disclosures that provide additional detail about those amounts. The new guidance is effective prospectively for fiscal years, and interim reporting periods within those years, beginning after December 15, 2012. The Company does not expect the adoption of these disclosure requirements to have a material impact on its consolidated financial statements. In February 2013, the FASB issued guidance requiring an entity to measure obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. The guidance also requires entities to disclose the nature and amount of the obligation as well as other information about the obligation. The new guidance is effective retrospectively for fiscal years, and interim reporting periods within those years, beginning after December 15, 2013. The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements. In December 2011, the FASB issued guidance requiring an entity to disclose the nature of its rights of setoff and related arrangements associated with its financial instruments and derivative instruments. The objective is to make financial statements that are prepared under GAAP more comparable to those prepared under International Financial Reporting Standards. The new disclosures will give financial statement users information about both gross and net exposures. In January 2013, the FASB issued an update and clarified the scope of transactions that are subject to disclosures concerning offsetting. These disclosure requirements are effective for annual reporting periods beginning on or after January 1, 2013, and interim periods within those annual periods, and should be applied retrospectively for all comparative periods presented. The Company does not expect the adoption of these disclosure requirements to have a material impact on its consolidated financial statements.
Fair value measurement	The Company has established a fair value hierarchy which prioritizes the inputs to the valuation techniques used to measure fair value into three levels. These levels are determined based on the lowest level input that is significant to the fair value measurement. Levels within the hierarchy are defined as follows: Level 1 - Unadjusted quoted prices in active markets for identical assets and liabilities; Level 2 - Quoted prices for similar assets and liabilities in active markets (other than those included in Level 1) which are observable, either directly or indirectly; and Level 3 - Valuations derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable.
Income tax uncertainties	The Company's policy classifies interest recognized on an underpayment of income taxes and any statutory penalties recognized on a tax position as tax expense and the balances at the end of a reporting period are recorded as part of the current or noncurrent reserve for uncertain income tax positions.

Disclosure of accounting policy for tax positions taken in the Company's tax return filed or to be filed for which it is more likely than not that the tax position will not be sustained upon examination by taxing authorities (i.e., uncertain tax positions) and other types of contingencies related to income taxes.

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