Recently Adopted and Recently Issued Accounting Guidance (Policies)	3 Months Ended
Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation. The Combined Financial Statements of Arconic Corporation are prepared in conformity with GAAP. In accordance with GAAP, certain situations require management to make estimates based on judgments and assumptions, which may affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements. These estimates are based on historical experience and, in some cases, assumptions based on current and future market experience, including considerations related to COVID-19. We have made our 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 Combined Financial Statements in future periods and potentially require adverse adjustments to the recoverability of goodwill and long-lived assets, the realizability of deferred tax assets and other judgments and estimations and assumptions that may be impacted by COVID-19.
Principles of Combination	Principles of Combination. The Combined Financial Statements of Arconic Corporation are prepared from ParentCo’s historical accounting records and are presented on a standalone basis as if the Arconic Corporation Businesses have been conducted independently from ParentCo. Such Combined Financial Statements include the historical operations that are considered to comprise the Arconic Corporation Businesses, as well as certain assets and liabilities that have been historically held at ParentCo’s corporate level but are specifically identifiable or otherwise attributable to Arconic Corporation. ParentCo’s net investment in these operations is reflected as Parent Company net investment on the accompanying Combined Financial Statements. All significant transactions and accounts within Arconic Corporation have been eliminated. All significant intercompany transactions between ParentCo and Arconic Corporation are included within Parent Company net investment on the accompanying Combined Financial Statements.
Cost Allocations	Cost Allocations. The Combined Financial Statements of Arconic Corporation include general corporate expenses of ParentCo that were not historically charged to the Arconic Corporation Businesses for certain support functions that are provided on a centralized basis, such as expenses related to finance, audit, legal, information technology, human resources, communications, compliance, facilities, employee benefits and compensation, and research and development activities. These general corporate expenses are included on the accompanying Statement of Combined Operations within Cost of goods sold, Selling, general administrative and other expenses, and Research and development expenses. These expenses have been allocated to Arconic Corporation on the basis of direct usage when identifiable, with the remainder allocated based on the Arconic Corporation Businesses’ segment revenue as a percentage of ParentCo’s total segment revenue, as reported in the respective periods. All external debt not directly attributable to Arconic Corporation has been excluded from the accompanying Combined Balance Sheet. Financing costs related to these debt obligations have been allocated to Arconic Corporation based on the ratio of capital invested by ParentCo in the Arconic Corporation Businesses to the total capital invested by ParentCo in both the Arconic Corporation Businesses and the Howmet Aerospace Businesses, and are included on the accompanying Statement of Combined Operations within Interest expense.
Recent Accounting Guidance	Adopted On January 1, 2020, Arconic Corporation adopted changes issued by the Financial Accounting Standards Board (FASB) to credit losses. This guidance added a new impairment model (known as the current expected credit loss (CECL) model), which is based on expected losses rather than incurred losses. Under this model, an entity is required to recognize an allowance equivalent to its estimate of expected credit losses. The CECL model applies to most debt instruments, trade receivables, lease receivables, financial guarantee contracts, and other loan commitments. This model does not have a minimum threshold for recognition of impairment losses and requires the measurement of expected credit losses on assets that have a low risk of loss. The adoption of this guidance did not have a material impact on the Combined Financial Statements. This guidance will need to be considered in future assessments of credit losses. Issued In March 2020, the FASB issued amendments that provide optional guidance to ease the potential burden of reference rate reform on financial reporting. Under the amendments, expedients and exceptions are provided for applying GAAP to contracts, hedging relationships, and other transactions affected by the reform, if certain criteria are met, and apply only to those transactions which reference LIBOR or another reference rate that is expected to be discontinued. 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 Combined Financial Statements.

Recently Adopted and Recently Issued Accounting Guidance (Policies)

3 Months Ended

Mar. 31, 2020

Basis of Presentation. The Combined Financial Statements of Arconic Corporation are prepared in conformity with GAAP. In accordance with GAAP, certain situations require management to make estimates based on judgments and assumptions, which may affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements. These estimates are based on historical experience and, in some cases, assumptions based on current and future market experience, including considerations related to COVID-19. We have made our 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 Combined Financial Statements in future periods and potentially require adverse adjustments to the recoverability of goodwill and long-lived assets, the realizability of deferred tax assets and other judgments and estimations and assumptions that may be impacted by COVID-19.

Principles of Combination

Principles of Combination. The Combined Financial Statements of Arconic Corporation are prepared from ParentCo’s historical accounting records and are presented on a standalone basis as if the Arconic Corporation Businesses have been conducted independently from ParentCo. Such Combined Financial Statements include the historical operations that are considered to comprise the Arconic Corporation Businesses, as well as certain assets and liabilities that have been historically held at ParentCo’s corporate level but are specifically identifiable or otherwise attributable to Arconic Corporation. ParentCo’s net investment in these operations is reflected as Parent Company net investment on the accompanying Combined Financial Statements. All significant transactions and accounts within Arconic Corporation have been eliminated. All significant intercompany transactions between ParentCo and Arconic Corporation are included within Parent Company net investment on the accompanying Combined Financial Statements.

Cost Allocations

Cost Allocations. The Combined Financial Statements of Arconic Corporation include general corporate expenses of ParentCo that were not historically charged to the Arconic Corporation Businesses for certain support functions that are provided on a centralized basis, such as expenses related to finance, audit, legal, information technology, human resources, communications, compliance, facilities, employee benefits and compensation, and research and development activities. These general corporate expenses are included on the accompanying Statement of Combined Operations within Cost of goods sold, Selling, general administrative and other expenses, and Research and development expenses. These expenses have been allocated to Arconic Corporation on the basis of direct usage when identifiable, with the remainder allocated based on the Arconic Corporation Businesses’ segment revenue as a percentage of ParentCo’s total segment revenue, as reported in the respective periods.

All external debt not directly attributable to Arconic Corporation has been excluded from the accompanying Combined Balance Sheet. Financing costs related to these debt obligations have been allocated to Arconic Corporation based on the ratio of capital invested by ParentCo in the Arconic Corporation Businesses to the total capital invested by ParentCo in both the Arconic Corporation Businesses and the Howmet Aerospace Businesses, and are included on the accompanying Statement of Combined Operations within Interest expense.

Recent Accounting Guidance

Adopted

On January 1, 2020, Arconic Corporation adopted changes issued by the Financial Accounting Standards Board (FASB) to credit losses. This guidance added a new impairment model (known as the current expected credit loss (CECL) model), which is based on expected losses rather than incurred losses. Under this model, an entity is required to recognize an allowance equivalent to its estimate of expected credit losses. The CECL model applies to most debt instruments, trade receivables, lease receivables, financial guarantee contracts, and other loan commitments. This model does not have a minimum threshold for recognition of impairment losses and requires the measurement of expected credit losses on assets that have a low risk of loss. The adoption of this guidance did not have a material impact on the Combined Financial Statements. This guidance will need to be considered in future assessments of credit losses.

Issued

In March 2020, the FASB issued amendments that provide optional guidance to ease the potential burden of reference rate reform on financial reporting. Under the amendments, expedients and exceptions are provided for applying GAAP to contracts, hedging relationships, and other transactions affected by the reform, if certain criteria are met, and apply only to those transactions which reference LIBOR or another reference rate that is expected to be discontinued. 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 Combined Financial Statements.