Proposed Separation Transaction	6 Months Ended
Jun. 30, 2016
Text Block [Abstract]
Proposed Separation Transaction	P. Proposed Separation Transaction – On September 28, 2015, Alcoa announced that its Board of Directors preliminarily approved a plan to separate into two standalone, publicly-traded companies. One company will be named Alcoa Corporation and will include the Alumina and Primary Metals segments and the Warrick, IN rolling operations and the equity interest in the rolling mill at the joint venture in Saudi Arabia, both of which are currently part of the Global Rolled Products segment. Alcoa, which will be re-named Arconic Inc., will continue to own the Global Rolled Products (except for the aforementioned rolling operations to be included in the future Alcoa Corporation company), Engineered Products and Solutions, and Transportation and Construction Solutions segments. Alcoa is targeting to complete the separation in the second half of 2016. The transaction is subject to a number of conditions, including, but not limited to, final approval by Alcoa’s Board of Directors; receipt of a private letter ruling from the Internal Revenue Service regarding certain U.S. federal income tax matters relating to the transaction; receipt of an opinion of legal counsel with respect to the tax-free nature of the transaction for U.S. federal income tax purposes; and the effectiveness of a Form 10 registration statement, which was filed with the U.S. Securities and Exchange Commission on June 29, 2016. Upon completion of the separation, Alcoa shareholders will own all of the outstanding shares of the future Arconic Inc. company, and each Alcoa shareholder as of the separation record date will own a pro rata share of the outstanding shares of the future Alcoa Corporation company to be distributed (up to 19.9% of such shares may be retained by the future Arconic Inc. company). Alcoa may, at any time and for any reason until the proposed transaction is complete, abandon the separation plan or modify or change its terms. In the 2016 second quarter and six-month period, Alcoa recognized $45 ($37 after-tax) and $63 ($54 after-tax), respectively, in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the proposed separation transaction.

P. Proposed Separation Transaction – On September 28, 2015, Alcoa announced that its Board of Directors preliminarily approved a plan to separate into two standalone, publicly-traded companies. One company will be named Alcoa Corporation and will include the Alumina and Primary Metals segments and the Warrick, IN rolling operations and the equity interest in the rolling mill at the joint venture in Saudi Arabia, both of which are currently part of the Global Rolled Products segment. Alcoa, which will be re-named Arconic Inc., will continue to own the Global Rolled Products (except for the aforementioned rolling operations to be included in the future Alcoa Corporation company), Engineered Products and Solutions, and Transportation and Construction Solutions segments.

Alcoa is targeting to complete the separation in the second half of 2016. The transaction is subject to a number of conditions, including, but not limited to, final approval by Alcoa’s Board of Directors; receipt of a private letter ruling from the Internal Revenue Service regarding certain U.S. federal income tax matters relating to the transaction; receipt of an opinion of legal counsel with respect to the tax-free nature of the transaction for U.S. federal income tax purposes; and the effectiveness of a Form 10 registration statement, which was filed with the U.S. Securities and Exchange Commission on June 29, 2016. Upon completion of the separation, Alcoa shareholders will own all of the outstanding shares of the future Arconic Inc. company, and each Alcoa shareholder as of the separation record date will own a pro rata share of the outstanding shares of the future Alcoa Corporation company to be distributed (up to 19.9% of such shares may be retained by the future Arconic Inc. company). Alcoa may, at any time and for any reason until the proposed transaction is complete, abandon the separation plan or modify or change its terms. In the 2016 second quarter and six-month period, Alcoa recognized $45 ($37 after-tax) and $63 ($54 after-tax), respectively, in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the proposed separation transaction.