Basis of Presentation	9 Months Ended
Sep. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation	A. Basis of Presentation – The interim Consolidated Financial Statements of Arconic Inc. (formerly known as Alcoa Inc. - see below) and its subsidiaries (“Arconic” or the “Company”) are unaudited. These Consolidated Financial Statements include all adjustments, consisting only of normal recurring adjustments, considered necessary by management to fairly state the Company’s results of operations, financial position, and cash flows. The results reported in these Consolidated Financial Statements are not necessarily indicative of the results that may be expected for the entire year. The 2015 year-end balance sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (GAAP). This Form 10-Q report should be read in conjunction with Arconic’s Annual Report on Form 10-K for the year ended December 31, 2015, which includes all disclosures required by GAAP. Certain amounts in previously issued financial statements were reclassified to conform to the current period presentation (see Note B). The separation of Alcoa Inc. into two standalone, publicly-traded companies, Arconic Inc. and Alcoa Corporation, (the “Separation Transaction”) became effective before the opening of the New York Stock Exchange (NYSE) on November 1, 2016 (see Note R). The accompanying unaudited, interim Consolidated Financial Statements include the historical results of Alcoa Corporation, as the Separation Transaction did not take place until November 1, 2016, after the most recent period reported in this Form 10-Q. In future filings, the historical results of the businesses that comprise Alcoa Corporation will be presented as discontinued operations in the Company’s Consolidated Financial Statements. As a result of the Separation Transaction, the accompanying unaudited, interim Consolidated Financial Statements are not indicative of the Company’s future financial position, results of operations or cash flows. Pursuant to the authorization provided at a special meeting of Arconic common shareholders held on October 5, 2016, shareholders approved a 1-for-3 reverse stock split of Arconic’s outstanding and authorized shares of common stock (the “Reverse Stock Split”). As a result of the Reverse Stock Split, every 3 shares of issued and outstanding common stock were combined into one issued and outstanding share of common stock, without any change in the par value per share. The Reverse Stock Split reduced the number of shares of common stock outstanding from approximately 1.3 billion shares to approximately 0.4 billion shares. The Company’s common stock began trading on a reverse stock split-adjusted basis on the NYSE on October 6, 2016. All share and per share data for all periods presented in this report has been retroactively restated to reflect the Reverse Stock Split (see Note M).

A. Basis of Presentation – The interim Consolidated Financial Statements of Arconic Inc. (formerly known as Alcoa Inc. - see below) and its subsidiaries (“Arconic” or the “Company”) are unaudited. These Consolidated Financial Statements include all adjustments, consisting only of normal recurring adjustments, considered necessary by management to fairly state the Company’s results of operations, financial position, and cash flows. The results reported in these Consolidated Financial Statements are not necessarily indicative of the results that may be expected for the entire year. The 2015 year-end balance sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (GAAP). This Form 10-Q report should be read in conjunction with Arconic’s Annual Report on Form 10-K for the year ended December 31, 2015, which includes all disclosures required by GAAP. Certain amounts in previously issued financial statements were reclassified to conform to the current period presentation (see Note B).

The separation of Alcoa Inc. into two standalone, publicly-traded companies, Arconic Inc. and Alcoa Corporation, (the “Separation Transaction”) became effective before the opening of the New York Stock Exchange (NYSE) on November 1, 2016 (see Note R).

The accompanying unaudited, interim Consolidated Financial Statements include the historical results of Alcoa Corporation, as the Separation Transaction did not take place until November 1, 2016, after the most recent period reported in this Form 10-Q. In future filings, the historical results of the businesses that comprise Alcoa Corporation will be presented as discontinued operations in the Company’s Consolidated Financial Statements. As a result of the Separation Transaction, the accompanying unaudited, interim Consolidated Financial Statements are not indicative of the Company’s future financial position, results of operations or cash flows.

Pursuant to the authorization provided at a special meeting of Arconic common shareholders held on October 5, 2016, shareholders approved a 1-for-3 reverse stock split of Arconic’s outstanding and authorized shares of common stock (the “Reverse Stock Split”). As a result of the Reverse Stock Split, every 3 shares of issued and outstanding common stock were combined into one issued and outstanding share of common stock, without any change in the par value per share. The Reverse Stock Split reduced the number of shares of common stock outstanding from approximately 1.3 billion shares to approximately 0.4 billion shares. The Company’s common stock began trading on a reverse stock split-adjusted basis on the NYSE on October 6, 2016. All share and per share data for all periods presented in this report has been retroactively restated to reflect the Reverse Stock Split (see Note M).