Contingencies and Commitments	12 Months Ended
Contingencies and Commitments	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Commitments	Contingencies and Commitments Contingencies Environmental Matters. Arconic participates in environmental assessments and cleanups at more than 100 locations. These include owned or operating facilities and adjoining properties, previously owned or operating facilities and adjoining properties, and waste sites, including Superfund (Comprehensive Environmental Response, Compensation and Liability Act (CERCLA)) sites. A liability is recorded for environmental remediation when a cleanup program becomes probable and the costs can be reasonably estimated. As assessments and cleanups proceed, the liability is adjusted based on progress made in determining the extent of remedial actions and related costs. The liability can change substantially due to factors such as the nature and extent of contamination, changes in remedial requirements, and technological changes, among others. Arconic’s remediation reserve balance was $230 at December 31, 2019 and $266 at December 31, 2018 recorded in Other noncurrent liabilities and deferred credits in the Consolidated Balance Sheet (of which $94 and $81, respectively, were classified as a current liability), and reflects the most probable costs to remediate identified environmental conditions for which costs can be reasonably estimated. Payments related to remediation expenses applied against the reserve were $65 in 2019 and $32 in 2018 and included expenditures currently mandated, as well as those not required by any regulatory authority or third party. The higher payments in 2019 compared with 2018 reflect the start of construction related to the Grasse River project. Arconic expects that trend to continue for 2020 as reflected by the increase in the portion of the reserve that is considered a current liability. Included in annual operating expenses are the recurring costs of managing hazardous substances and environmental programs. These costs are estimated to be approximately 1% or less of Cost of goods sold. The following discussion provides details regarding the current status of the most significant remediation reserves related to a current Arconic site. Massena West, NY—Arconic has an ongoing remediation project related to the Grasse River, which is adjacent to Arconic’s Massena plant site. Many years ago, it was determined that sediments and fish in the river contain varying levels of polychlorinated biphenyls (PCBs). The project, which was selected by the U.S. Environmental Protection Agency (EPA) in a Record of Decision issued in April 2013, is aimed at capping PCB contaminated sediments with concentration in excess of one part per million in the main channel of the river and dredging PCB contaminated sediments in the near-shore areas where total PCBs exceed one part per million. At December 31, 2019 and 2018, the reserve balances associated with this matter were $171 and $198, respectively. In the first quarter of 2019, Arconic received approval from the EPA of its final remedial design which is now under construction and is expected to be completed in 2022. During the second quarter of 2019, Arconic recorded a charge of $25 due to changes required in the remedial design and post-construction monitoring. As the project proceeds, the liability may be updated due to factors such as changes in remedial requirements, site restoration costs, and ongoing operation and maintenance costs, among others. Tax. Pursuant to the Tax Matters Agreement, dated as of October 31, 2016, entered into between the Company and Alcoa Corporation in connection with the Separation of Alcoa, the Company shares responsibility with Alcoa Corporation for, and Alcoa Corporation has agreed to partially indemnify the Company with respect to the following matter. As previously reported, in July 2013, following a Spanish corporate income tax audit covering the 2006 through 2009 tax years, an assessment was received mainly disallowing certain interest deductions claimed by a Spanish consolidated tax group owned by the Company. In August 2013, the Company filed an appeal of this assessment in Spain’s Central Tax Administrative Court, which was denied in January 2015. Arconic filed another appeal in Spain’s National Court in March 2015 which was denied in July 2018. The National Court’s decision requires the assessment for the 2006 through 2009 tax years to be reissued to take into account the outcome of the 2003 to 2005 audit which was closed in 2017. The Company estimates the revised assessment to be $172 (€154), including interest. In March 2019, the Supreme Court of Spain accepted the Company's petition to review the National Court’s decision, and the Company has filed a formal appeal of the assessment. The Supreme Court is reviewing the assessment on its merits and will render a final decision. In the event the Company receives an unfavorable ruling from the Supreme Court of Spain, a portion of the assessment may be offset with existing net operating losses and tax credits available to the Spanish consolidated tax group, which would be shared between the Company and Alcoa Corporation as provided for in the Tax Matters Agreement. In the third quarter of 2018, Arconic established an income tax reserve and an indemnification receivable representing Alcoa Corporation’s 49% share of the liability. As of the end of 2019, the balances of the reserve, including interest, and the receivable are $59 million (€53 million) and $29 million (€26 million), respectively. Additionally, while the tax years 2010 through 2013 are closed to audit, it is possible that the Company may receive assessments for tax years subsequent to 2013. Any potential assessment for an individual tax year is not expected to be material to the Company’s consolidated operations. Reynobond PE. As previously reported, on June 13, 2017, the Grenfell Tower in London, U.K. caught fire resulting in fatalities, injuries and damage. A French subsidiary of Arconic, Arconic Architectural Products SAS (AAP SAS), supplied a product, Reynobond PE, to its customer, a cladding system fabricator, which used the product as one component of the overall cladding system on Grenfell Tower. The fabricator supplied its portion of the cladding system to the façade installer, who then completed and installed the system under the direction of the general contractor. Neither Arconic nor AAP SAS was involved in the design or installation of the system used at the Grenfell Tower, nor did it have a role in any other aspect of the building’s refurbishment or original design. Regulatory investigations into the overall Grenfell Tower matter are being conducted, including a criminal investigation by the London Metropolitan Police Service (the “Police”), a Public Inquiry by the British government and a consumer protection inquiry by a French public authority. The Public Inquiry was announced by the U.K. Prime Minister on June 15, 2017 and subsequently was authorized to examine the circumstances leading up to and surrounding the Grenfell Tower fire in order to make findings of fact and recommendations to the U.K. Government on matters such as the design, construction and modification of the building, the role of relevant public authorities and contractors, the implications of the fire for the adequacy and enforcement of relevant regulations, arrangements in place for handling emergencies and the handling of concerns from residents, among other things. Hearings for Phase 1 of the Public Inquiry began on May 21, 2018 and concluded on December 12, 2018. Phase 2 hearings of the Public Inquiry began in early 2020, following which a final report will be written and subsequently published. AAP SAS is participating as a Core Participant in the Public Inquiry and is also cooperating with the ongoing parallel investigation by the Police. The Company no longer sells the PE product for architectural use on buildings. Given the preliminary nature of these investigations and the uncertainty of potential future litigation, the Company cannot reasonably estimate at this time the likelihood of an unfavorable outcome or the possible loss or range of losses in the event of an unfavorable outcome. Behrens et al. v. Arconic Inc. et al. As previously reported, on June 6, 2019, 247 plaintiffs comprised of survivors and estates of decedents of the Grenfell Tower fire filed a complaint against “Arconic Inc., Alcoa Inc. and Arconic Architectural Products, LLC” (collectively, for purposes of the description of such proceeding, the “Arconic Defendants”), as well as Saint-Gobain Corporation, d/b/a Celotex and Whirlpool Corporation, in the Court of Common Pleas of Philadelphia County. The complaint alleges claims under Pennsylvania state law for products liability and wrongful death related to the fire. In particular, the plaintiffs allege that the Arconic Defendants knowingly supplied a dangerous product (Reynobond PE) for installation on the Grenfell Tower despite knowing that Reynobond PE was unfit for use above a certain height. The Arconic Defendants removed the case to the United States District Court for the Eastern District of Pennsylvania on June 19, 2019. On August 29, 2019, the Arconic Defendants moved to dismiss the complaint on the bases, among other things, that: (i) the case should be heard in the United Kingdom, not the United States; (ii) there is no jurisdiction over necessary parties; and (iii) Pennsylvania products liability law does not apply to manufacture and sale of product overseas. On December 23, 2019, the Court issued an order denying the motion to dismiss the complaint on bases (ii) and (iii) and suggesting a procedure for limited discovery followed by further briefing on those subjects. Discovery is ongoing on defendants’ motion to have the case dismissed in favor of a UK forum (forum non conveniens). On January 23, 2020, the Court ordered that the parties complete discovery relating to forum non conveniens by March 16, 2020, and that briefing conclude on April 13, 2020. The Court will hold oral argument on this motion on May 7, 2020. Given the preliminary nature of this matter and the uncertainty of litigation, the Company cannot reasonably estimate at this time the likelihood of an unfavorable outcome or the possible loss or range of losses in the event of an unfavorable outcome. Howard v. Arconic Inc. et al. As previously reported, a purported class action complaint related to the Grenfell Tower fire was filed on August 11, 2017 in the United States District Court for the Western District of Pennsylvania against Arconic Inc. and Klaus Kleinfeld. A related purported class action complaint was filed in the United States District Court for the Western District of Pennsylvania on September 15, 2017, under the caption Sullivan v. Arconic Inc. et al., against Arconic Inc., three former Arconic executives, several current and former Arconic directors, and banks that acted as underwriters for Arconic’s September 18, 2014 preferred stock offering (the “Preferred Offering”). The plaintiff in Sullivan had previously filed a purported class action against the same defendants on July 18, 2017 in the Southern District of New York and, on August 25, 2017, voluntarily dismissed that action without prejudice. On February 7, 2018, on motion from certain putative class members, the court consolidated Howard and Sullivan, closed Sullivan, and appointed lead plaintiffs in the consolidated case. On April 9, 2018, the lead plaintiffs in the consolidated purported class action filed a consolidated amended complaint. The consolidated amended complaint alleged that the registration statement for the Preferred Offering contained false and misleading statements and omitted to state material information, including by allegedly failing to disclose material uncertainties and trends resulting from sales of Reynobond PE for unsafe uses and by allegedly expressing a belief that appropriate risk management and compliance programs had been adopted while concealing the risks posed by Reynobond PE sales. The consolidated amended complaint also alleged that between November 4, 2013 and June 23, 2017 Arconic and Kleinfeld made false and misleading statements and failed to disclose material information about the Company’s commitment to safety, business and financial prospects, and the risks of the Reynobond PE product, including in Arconic’s Form 10-Ks for the fiscal years ended December 31, 2013, 2014, 2015, and 2016, its Form 10-Qs and quarterly financial press releases from the fourth quarter of 2013 through the first quarter of 2017, its 2013, 2014, 2015, and 2016 Annual Reports, its 2016 Annual Highlights Report, and on its official website. The consolidated amended complaint sought, among other things, unspecified compensatory damages and an award of attorney and expert fees and expenses. On June 8, 2018, all defendants moved to dismiss the consolidated amended complaint for failure to state a claim. On June 21, 2019, the Court granted the defendants’ motion to dismiss in full, dismissing the consolidated amended complaint in its entirety without prejudice. On July 23, 2019, the lead plaintiffs filed a second amended complaint. The second amended complaint alleges generally the same claims as the consolidated amended complaint with certain additional allegations, as well as claims that the risk factors set forth in the registration statement for the Preferred Offering were inadequate and that certain additional statements in the sources identified above were misleading. The second amended complaint seeks, among other things, unspecified compensatory damages and an award of attorney and expert fees and expenses. On September 11, 2019, all defendants moved to dismiss the second amended complaint. Plaintiffs’ opposition to that motion was filed by November 1, 2019 and all defendants filed a reply brief on November 26, 2019. Given the preliminary nature of this matter and the uncertainty of litigation, the Company cannot reasonably estimate at this time the likelihood of an unfavorable outcome or the possible loss or range of losses in the event of an unfavorable outcome. Raul v. Albaugh, et al. As previously reported, on June 22, 2018, a derivative complaint was filed nominally on behalf of Arconic by a purported Arconic stockholder against the then members of Arconic’s Board of Directors and Klaus Kleinfeld and Ken Giacobbe, naming Arconic as a nominal defendant, in the United States District Court for the District of Delaware. The complaint raises similar allegations as the consolidated amended complaint and second amended complaint in Howard, as well as allegations that the defendants improperly authorized the sale of Reynobond PE for unsafe uses, and asserts claims under Section 14(a) of the Exchange Act and Delaware state law. On July 13, 2018, the parties filed a stipulation agreeing to stay this case until the final resolution of the Howard case, the Grenfell Tower Public Inquiry in London, and the investigation by the Police and on July 23, 2018, the Court approved the stay. Given the preliminary nature of this matter and the uncertainty of litigation, the Company cannot reasonably estimate at this time the likelihood of an unfavorable outcome or the possible loss or range of losses in the event of an unfavorable outcome. While the Company believes that these cases are without merit and intends to challenge them vigorously, there can be no assurances regarding the ultimate resolution of these matters. Stockholder Demands. As previously noted, the Board of Directors also received letters, purportedly sent on behalf of stockholders, reciting allegations similar to those made in the federal court lawsuits and demanding that the Board authorize the Company to initiate litigation against members of management, the Board and others. The Board of Directors appointed a Special Litigation Committee of the Board to review, investigate, and make recommendations to the Board regarding the appropriate course of action with respect to these stockholder demand letters. On May 22, 2019, the Special Litigation Committee, following completion of its investigation into the claims demanded in the demand letters, recommended to the Board that it reject the demands to authorize commencement of litigation. On May 28, 2019, the Board adopted the Special Litigation Committee’s findings and recommendations and rejected the demands that it authorize commencement of actions to assert the claims set forth in the demand letters. Other. In addition to the matters discussed above, various other lawsuits, claims, and proceedings have been or may be instituted or asserted against Arconic, including those pertaining to environmental, product liability, safety and health, employment, tax and antitrust matters. While the amounts claimed in these other matters may be substantial, the ultimate liability cannot currently be determined because of the considerable uncertainties that exist. Therefore, it is possible that the Company’s liquidity or results of operations in a period could be materially affected by one or more of these other matters. However, based on facts currently available, management believes that the disposition of these other matters that are pending or asserted will not have a material adverse effect, individually or in the aggregate, on the results of operations, financial position or cash flows of the Company. Commitments Purchase Obligations. Arconic has entered into purchase commitments for raw materials, energy and other goods and services, which total $604 in 2020, $93 in 2021, $45 in 2022, $12 in 2023, $4 in 2024, and $2 thereafter. Operating Leases. See Note O for the operating lease future minimum contractual obligations. Guarantees. At December 31, 2019, Arconic had outstanding bank guarantees related to tax matters, outstanding debt, workers’ compensation, environmental obligations, energy contracts, and customs duties, among others. The total amount committed under these guarantees, which expire at various dates between 2020 and 2040 was $31 at December 31, 2019. Pursuant to the Separation and Distribution Agreement between Arconic and Alcoa Corporation, Arconic was required to provide certain guarantees for Alcoa Corporation, which had a combined fair value of $9 and $6 at December 31, 2019 and 2018, respectively, and were included in Other noncurrent liabilities and deferred credits on the accompanying Consolidated Balance Sheet. Furthermore, Arconic was required to provide guarantees related to two long-term supply agreements for energy for Alcoa Corporation facilities in the event of an Alcoa Corporation payment default. In October 2017, Alcoa Corporation announced that it had terminated one of the two agreements, the electricity contract with Luminant Generation Company LLC that was tied to its Rockdale Operations, effective as of October 1, 2017. As a result of the termination of the Rockdale electricity contract, Arconic recorded income of $25 in the fourth quarter of 2017 associated with reversing the fair value of the electricity contract guarantee. For the remaining long-term supply agreement, Arconic is required to provide a guarantee up to an estimated present value amount of approximately $1,353 and $1,087 at December 31, 2019 and December 31, 2018, respectively, in the event of an Alcoa Corporation payment default. This guarantee expires in 2047. For this guarantee, subject to its provisions, Arconic is secondarily liable in the event of a payment default by Alcoa Corporation. Arconic currently views the risk of an Alcoa Corporation payment default on its obligations under the contract to be remote. In December 2019, Arconic entered into a one-year insurance policy with a limit of $80 relating to the remaining long-term energy supply agreement. The premium is expected to be paid by Alcoa Corporation. The decision to enter into a claims purchase agreement or insurance policy will be made on an annual basis going forward. Letters of Credit. Arconic has outstanding letters of credit, primarily related to workers’ compensation, environmental obligations and leasing obligations. The total amount committed under these letters of credit, which automatically renew or expire at various dates, mostly in 2020, was $142 at December 31, 2019. Pursuant to the Separation and Distribution Agreement, Arconic was required to retain letters of credit of $52 that had previously been provided related to both Arconic and Alcoa Corporation workers’ compensation claims which occurred prior to November 1, 2016. Alcoa Corporation workers’ compensation claims and letter of credit fees paid by Arconic are being proportionally billed to and are being fully reimbursed by Alcoa Corporation. Surety Bonds. Arconic has outstanding surety bonds primarily related to tax matters, contract performance, workers’ compensation, environmental-related matters, and customs duties. The total amount committed under these surety bonds, which expire at various dates, primarily in 2020, was $50 at December 31, 2019. Pursuant to the Separation and Distribution Agreement, Arconic was required to provide surety bonds related to Alcoa Corporation workers’ compensation claims which occurred prior to November 1, 2016 and, as a result, Arconic has $24 in outstanding surety bonds relating to these liabilities. Alcoa Corporation workers’ compensation claims and surety bond fees paid by Arconic are being proportionately billed to and that portion billed is being fully reimbursed by Alcoa Corporation.