Proposed Separation Transaction	3 Months Ended
Mar. 31, 2016
Text Block [Abstract]
Proposed Separation Transaction	O. Proposed Separation Transaction – On September 28, 2015, Alcoa announced that its Board of Directors approved a plan to separate into two independent, publicly-traded companies: An Upstream Company, the new Alcoa, that will primarily comprise the Alumina and Primary Metals segments; and a Value-Add Company, Arconic, that will principally include the Global Rolled Products, Engineered Products and Solutions, and Transportation and Construction Solutions segments. The Company currently plans that upon separation, which is targeted in the second half of 2016, the new Alcoa will also become owner of the rolling mill at the Warrick, IN Operations and the stake in the Ma’aden Rolling Company in Saudi Arabia. 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 favorable 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 to be filed with the U.S. Securities and Exchange Commission. Upon completion of the separation, Alcoa shareholders will own all of the outstanding shares of both companies. 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. For the first quarter of 2016, Alcoa recognized $18 ($17 after-tax) in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the proposed transaction.

O. Proposed Separation Transaction – On September 28, 2015, Alcoa announced that its Board of Directors approved a plan to separate into two independent, publicly-traded companies: An Upstream Company, the new Alcoa, that will primarily comprise the Alumina and Primary Metals segments; and a Value-Add Company, Arconic, that will principally include the Global Rolled Products, Engineered Products and Solutions, and Transportation and Construction Solutions segments. The Company currently plans that upon separation, which is targeted in the second half of 2016, the new Alcoa will also become owner of the rolling mill at the Warrick, IN Operations and the stake in the Ma’aden Rolling Company in Saudi Arabia.

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 favorable 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 to be filed with the U.S. Securities and Exchange Commission. Upon completion of the separation, Alcoa shareholders will own all of the outstanding shares of both companies. 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. For the first quarter of 2016, Alcoa recognized $18 ($17 after-tax) in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the proposed transaction.