Basis of Presentation (Policies)	9 Months Ended
Basis of Presentation (Policies)	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The interim Consolidated Financial Statements of Howmet Aerospace Inc. (formerly known as Arconic Inc.) and subsidiaries (“Howmet” 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 2020 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 the Company's Annual Report on Form 10-K for the year ended December 31, 2020, which includes all disclosures required by GAAP. Certain amounts in previously issued financial statements were reclassified to conform to the current period presentation. The separation of Arconic Inc. into two standalone, publicly-traded companies, Howmet Aerospace Inc. and Arconic Corporation, (the “Arconic Inc. Separation Transaction”) occurred on April 1, 2020. The financial results of Arconic Corporation for all periods prior to the Arconic Inc. Separation Transaction have been retrospectively reflected in the Statement of Consolidated Operations as discontinued operations and, as such, have been excluded from continuing operations and segment results for all periods presented. The cash flows, comprehensive income, and equity related to Arconic Corporation have not been segregated and are included in the Statement of Consolidated Cash Flows, Statement of Consolidated Comprehensive Income, and Statement of Changes in Consolidated Equity, respectively, for all periods prior to the Arconic Inc. Separation Transaction. See Note B for additional information related to the Arconic Inc. Separation Transaction and discontinued operations. For the nine months ended September 30, 2021 and 2020, the Company derived approximately 60% and 70%, respectively, of its revenue from products sold to the aerospace end-market. As a result of the global COVID-19 pandemic and its impact on the aerospace industry to-date, the possibility exists that there could be a sustained impact to our operations and financial results. Since the start of the pandemic, certain original equipment manufacturer (“OEM”) customers have reduced production or suspended manufacturing operations in North America and Europe on a temporary basis. While the pandemic resulted in the temporary closure of a small number of the Company's manufacturing facilities during 2020, all of our manufacturing facilities are currently operating. Since the duration of the pandemic is uncertain, management has taken a series of actions to address the financial impact, including fixed and variable cost reductions, such as headcount reductions in certain segments, and reducing the level of capital expenditures to preserve cash and maintain liquidity. The preparation of the Consolidated Financial Statements of the Company in conformity with GAAP requires management to make certain judgments, estimates, and assumptions. These estimates are based on historical experience and, in some cases, assumptions based on current and future market experience, including considerations relating to the impact of COVID-19. The impact of COVID-19 is rapidly changing and of unknown duration and macroeconomic impact and, as a result, these considerations remain highly uncertain. Management has made its best estimates using all relevant information available at the time, but it is possible that our estimates will differ from our actual results and affect the Consolidated Financial Statements in future periods and potentially require adverse adjustments to the recoverability of goodwill, intangible and long-lived assets, the realizability of deferred tax assets and other judgments and estimations and assumptions that may be impacted by COVID-19.
Recently Adopted and Recently Issued Accounting Guidance	Recently Adopted and Recently Issued Accounting Guidance Adopted On January 1, 2021, the Company adopted changes issued by the Financial Accounting Standards Board (“FASB”) that were intended to simplify various aspects of accounting for income taxes by eliminating certain exceptions contained in existing guidance and amending other guidance to simplify several other income tax accounting matters. The adoption of this new guidance did not have a material impact on the Consolidated Financial Statements. Issued In March 2020, the FASB issued amendments that provide optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform, if certain criteria are met. The amendments apply only to contracts and hedging relationships that reference London Inter-bank Offered Rate (“LIBOR”) or another reference rate expected to be discontinued due to reference rate reform. These amendments are effective immediately and may be applied prospectively to contract modifications made and hedging relationships entered into or evaluated on or before December 31, 2022. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements.
Earnings Per Share	Basic earnings per share (“EPS”) amounts are computed by dividing earnings, after the deduction of preferred stock dividends declared, by the average number of common shares outstanding. Diluted EPS amounts assume the issuance of common stock for all potentially dilutive share equivalents outstanding.