NEW MARKETS TAX CREDIT TRANSACTIONS	12 Months Ended
Aug. 31, 2016
Income Tax Disclosure [Abstract]
New Markets Tax Credit Transactions	NOTE 12. NEW MARKETS TAX CREDIT TRANSACTIONS In the second quarter of fiscal 2016, the Company entered into a financing transaction with U.S. Bancorp Community Development Corporation, a Minnesota corporation ("USBCDC"), related to the development, construction and equipping of a steel micro-mill in Durant, Oklahoma. To effect the transaction, USBCDC made a capital contribution to USBCDC Investment Fund 156, LLC, a Missouri limited liability company (the "Investment Fund"). Additionally, Commonwealth Acquisitions Holdings, Inc., a wholly owned subsidiary of CMC ("Commonwealth"), made a loan to the Investment Fund. The transaction qualified under the NMTC Program provided for in the Act. The NMTC Program is intended to induce capital investment in qualified low-income communities. The Act permits taxpayers to claim credits against federal income taxes for up to 39% of qualified investments in certain CDEs. CDEs are privately managed entities that are certified to make qualified low-income community investments to qualified projects. Commonwealth loaned $35.3 million to the Investment Fund at an interest rate of approximately 1.08% per year and with a maturity date of December 24, 2045 (the "Commonwealth Loan"). The Investment Fund also received capital contributions from USBCDC in the aggregate amount of $17.7 million (the "USBCDC Equity"). The Investment Fund used $51.5 million of the proceeds received from the Commonwealth Loan and the USBCDC Equity to make qualified equity investments ("QEIs") into certain CDEs, which, in turn, used $50.7 million of the QEIs to make loans to CMC Steel Oklahoma, LLC, a wholly owned subsidiary of CMC, with terms similar to the Commonwealth Loan and as partial financing for the construction, development and equipping of a new steel micro-mill in Durant, Oklahoma. The proceeds of the loans from the CDEs were recorded as restricted cash and included in other current assets in the accompanying consolidated balance sheet. During fiscal year 2016, the Company spent $27.2 million for qualified construction, development, and equipping activities for the micro-mill. The balance remaining in restricted cash was $21.7 million at August 31, 2016. By virtue of its capital contribution to the Investment Fund, USBCDC is entitled to substantially all of the benefits derived from the new markets tax credits ("NMTCs"). This transaction includes a put/call provision whereby the Company may be obligated or entitled to repurchase USBCDC's interest in the Investment Fund. The Company believes USBCDC will exercise the put option in December 2022 at the end of the recapture period. The value attributed to the put/call is de minimis. The NMTC is subject to 100% recapture for a period of seven years as provided in the Internal Revenue Code. The Company is required to be in compliance with various regulations and contractual provisions that apply to the NMTC Program. Non-compliance with applicable requirements could result in projected tax benefits not being realized and, therefore, could require the Company to indemnify USBCDC for any loss or recapture of NMTCs related to the financing until such time as the Company's obligation to deliver tax benefits is relieved. The Company does not anticipate any credit recaptures will be required in connection with this arrangement. The Company has determined that the Investment Fund is a VIE, of which the Company is the primary beneficiary and has consolidated it in accordance with the accounting standard for consolidation. USBCDC's contribution is included in other long-term liabilities in the accompanying consolidated balance sheet. Direct costs incurred in structuring the financing arrangement are deferred and will be recognized as expense over the seven year recapture period. Incremental costs to maintain the structure during the compliance period are recognized as incurred.

NOTE 12. NEW MARKETS TAX CREDIT TRANSACTIONS

In the second quarter of fiscal 2016, the Company entered into a financing transaction with U.S. Bancorp Community Development Corporation, a Minnesota corporation ("USBCDC"), related to the development, construction and equipping of a steel micro-mill in Durant, Oklahoma. To effect the transaction, USBCDC made a capital contribution to USBCDC Investment Fund 156, LLC, a Missouri limited liability company (the "Investment Fund"). Additionally, Commonwealth Acquisitions Holdings, Inc., a wholly owned subsidiary of CMC ("Commonwealth"), made a loan to the Investment Fund. The transaction qualified under the NMTC Program provided for in the Act. The NMTC Program is intended to induce capital investment in qualified low-income communities. The Act permits taxpayers to claim credits against federal income taxes for up to 39% of qualified investments in certain CDEs. CDEs are privately managed entities that are certified to make qualified low-income community investments to qualified projects.

Commonwealth loaned $35.3 million to the Investment Fund at an interest rate of approximately 1.08% per year and with a maturity date of December 24, 2045 (the "Commonwealth Loan"). The Investment Fund also received capital contributions from USBCDC in the aggregate amount of $17.7 million (the "USBCDC Equity"). The Investment Fund used $51.5 million of the proceeds received from the Commonwealth Loan and the USBCDC Equity to make qualified equity investments ("QEIs") into certain CDEs, which, in turn, used $50.7 million of the QEIs to make loans to CMC Steel Oklahoma, LLC, a wholly owned subsidiary of CMC, with terms similar to the Commonwealth Loan and as partial financing for the construction, development and equipping of a new steel micro-mill in Durant, Oklahoma. The proceeds of the loans from the CDEs were recorded as restricted cash and included in other current assets in the accompanying consolidated balance sheet. During fiscal year 2016, the Company spent $27.2 million for qualified construction, development, and equipping activities for the micro-mill. The balance remaining in restricted cash was $21.7 million at August 31, 2016.

By virtue of its capital contribution to the Investment Fund, USBCDC is entitled to substantially all of the benefits derived from the new markets tax credits ("NMTCs"). This transaction includes a put/call provision whereby the Company may be obligated or entitled to repurchase USBCDC's interest in the Investment Fund. The Company believes USBCDC will exercise the put option in December 2022 at the end of the recapture period. The value attributed to the put/call is de minimis. The NMTC is subject to 100% recapture for a period of seven years as provided in the Internal Revenue Code. The Company is required to be in compliance with various regulations and contractual provisions that apply to the NMTC Program. Non-compliance with applicable requirements could result in projected tax benefits not being realized and, therefore, could require the Company to indemnify USBCDC for any loss or recapture of NMTCs related to the financing until such time as the Company's obligation to deliver tax benefits is relieved. The Company does not anticipate any credit recaptures will be required in connection with this arrangement.

The Company has determined that the Investment Fund is a VIE, of which the Company is the primary beneficiary and has consolidated it in accordance with the accounting standard for consolidation. USBCDC's contribution is included in other long-term liabilities in the accompanying consolidated balance sheet. Direct costs incurred in structuring the financing arrangement are deferred and will be recognized as expense over the seven year recapture period. Incremental costs to maintain the structure during the compliance period are recognized as incurred.