Separation Transaction	9 Months Ended
Sep. 30, 2016
Text Block [Abstract]
Separation Transaction	R. Separation Transaction – On September 28, 2015, Arconic 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 Inc., 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 Alcoa Corporation), Engineered Products and Solutions, and Transportation and Construction Solutions segments. On September 29, 2016, the Board approved the completion of the Separation Transaction by means of a pro rata distribution (the “Distribution”) by the Company on November 1, 2016 of 80.1 percent of the outstanding common stock of Alcoa Corporation to Company shareholders of record as of the close of business on October 20, 2016 (the “Record Date”). Arconic will retain 19.9 percent of the Alcoa Corporation common stock. On November 1, 2016, the Separation Transaction was completed and became effective before the opening of the NYSE. In the Distribution, each Company shareholder received one share of Alcoa Corporation common stock for every three shares of the Company’s common stock held as of the close of business on the Record Date. Shareholders received cash in lieu of fractional shares of Alcoa Corporation common stock. In connection with the Separation Transaction, at the end of October 2016, the Company entered into certain agreements with Alcoa Corporation to implement the legal and structural separation between the two companies, govern the relationship between the Company and Alcoa Corporation after the completion of the Separation Transaction, and allocate between the Company and Alcoa Corporation various assets, liabilities and obligations, including, among other things, employee benefits, environmental liabilities, intellectual property, and tax-related assets and liabilities. These agreements included a Separation and Distribution Agreement, Tax Matters Agreement, Employee Matters Agreement, Transition Services Agreement and certain Patent, Know-How, Trade Secret License and Trademark License Agreements. In the 2016 third quarter and nine-month period, Arconic recognized $55 ($44 after-tax) and $118 ($98 after-tax), respectively, in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the Separation Transaction. In addition, Arconic also incurred capital expenditures and debt issuance costs (see Note I) of $60 in the third quarter and $81 in the nine-month period of 2016 related to the separation. Inception to date costs recorded in Selling, general administrative, and other expenses were $142 as well as capital expenditures and debt issuance costs of $81.

R. Separation Transaction – On September 28, 2015, Arconic 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 Inc., 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 Alcoa Corporation), Engineered Products and Solutions, and Transportation and Construction Solutions segments.

On September 29, 2016, the Board approved the completion of the Separation Transaction by means of a pro rata distribution (the “Distribution”) by the Company on November 1, 2016 of 80.1 percent of the outstanding common stock of Alcoa Corporation to Company shareholders of record as of the close of business on October 20, 2016 (the “Record Date”). Arconic will retain 19.9 percent of the Alcoa Corporation common stock. On November 1, 2016, the Separation Transaction was completed and became effective before the opening of the NYSE. In the Distribution, each Company shareholder received one share of Alcoa Corporation common stock for every three shares of the Company’s common stock held as of the close of business on the Record Date. Shareholders received cash in lieu of fractional shares of Alcoa Corporation common stock.

In connection with the Separation Transaction, at the end of October 2016, the Company entered into certain agreements with Alcoa Corporation to implement the legal and structural separation between the two companies, govern the relationship between the Company and Alcoa Corporation after the completion of the Separation Transaction, and allocate between the Company and Alcoa Corporation various assets, liabilities and obligations, including, among other things, employee benefits, environmental liabilities, intellectual property, and tax-related assets and liabilities. These agreements included a Separation and Distribution Agreement, Tax Matters Agreement, Employee Matters Agreement, Transition Services Agreement and certain Patent, Know-How, Trade Secret License and Trademark License Agreements.

In the 2016 third quarter and nine-month period, Arconic recognized $55 ($44 after-tax) and $118 ($98 after-tax), respectively, in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the Separation Transaction. In addition, Arconic also incurred capital expenditures and debt issuance costs (see Note I) of $60 in the third quarter and $81 in the nine-month period of 2016 related to the separation. Inception to date costs recorded in Selling, general administrative, and other expenses were $142 as well as capital expenditures and debt issuance costs of $81.