Proposed Separation Transaction	12 Months Ended
Dec. 31, 2015
Text Block [Abstract]
Proposed Separation Transaction	Y. 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. One company will comprise the Alumina and Primary Metals segments and the other company will comprise the Global Rolled Products, 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 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. In 2015, Alcoa recognized $24 (pre- and after-tax) in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the proposed separation transaction.

Y. 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. One company will comprise the Alumina and Primary Metals segments and the other company will comprise the Global Rolled Products, 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 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. In 2015, Alcoa recognized $24 (pre- and after-tax) in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the proposed separation transaction.