Recently Adopted and Recently Issued Accounting Guidance	3 Months Ended
Mar. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Recently Adopted and Recently Issued Accounting Guidance	B. Recently Adopted and Recently Issued Accounting Guidance Adopted In March 2016, the Financial Accounting Standards Board (“FASB”) issued changes to employee share-based payment accounting. Previously, an entity determined for each share-based payment award whether the difference between the deduction for tax purposes and the compensation cost recognized for financial reporting purposes resulted in either an excess tax benefit or a tax deficiency. Excess tax benefits were recognized in additional paid-in capital; tax deficiencies were recognized either as an offset to accumulated excess tax benefits, if any, or in the income statement. Excess tax benefits were not recognized until the deduction reduced taxes payable. The changes require all excess tax benefits and tax deficiencies related to share-based payment awards to be recognized as income tax expense or benefit in the income statement. The tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur. An entity also should recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. Additionally, the presentation of excess tax benefits related to share-based payment awards in the statement of cash flows changed. Previously, excess tax benefits were separated from other income tax cash flows and classified as a financing activity. The changes require excess tax benefits to be classified along with other income tax cash flows as an operating activity. Also, the changes require cash paid by an employer when directly withholding shares for tax-withholding purposes to be classified as a financing activity. Additionally, for a share-based award to qualify for equity classification it previously could not be partially settled in cash in excess of the employer’s minimum statutory withholding requirements. The changes permit equity classification of share-based awards for withholdings up to the maximum statutory tax rates in applicable jurisdictions. These changes became effective for Arconic on January 1, 2017. Management has concluded that the adoption of this guidance did not have a material effect on the Consolidated Financial Statements. In March 2016, the FASB issued changes eliminating the requirement for an investor to adjust an equity method investment, results of operations, and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held as a result of an increase in the level of ownership interest or degree of influence. Additionally, an entity that has an available-for-sale equity security that becomes qualified for the equity method of accounting must recognize through earnings the unrealized holding gain or loss in accumulated other comprehensive income at the date the investment becomes qualified for use of the equity method. These changes became effective for Arconic on January 1, 2017. Management has concluded that the adoption of this guidance did not have a material impact on the Consolidated Financial Statements. In March 2016, the FASB issued changes to derivative instruments designated as hedging instruments. These changes clarify that a change in the counterparty to a derivative instrument that has been designated as a hedging instrument does not, in and of itself, require dedesignation of that hedging relationship provided that all other hedge accounting criteria continue to be met. These changes became effective for Arconic on January 1, 2017. Management has determined that the adoption of this guidance did not have a material impact on the Consolidated Financial Statements. In October 2016, the FASB issued changes to the accounting for Intra-Entity transactions, other than inventory. Previously, no immediate tax impact was recognized in the consolidated financial statements as a result of intra-entity transfers of assets. The previous standard precluded an entity from reflecting a tax benefit or expense from an intra-entity transfer between entities that file separate tax returns, whether or not such entities were in different tax jurisdictions, until the asset was sold to a third party or otherwise recovered. The previous standard also prohibited recognition by the buyer of a deferred tax asset for the temporary difference arising from the excess of the buyer’s tax basis over the cost to the seller. The changes require the current and deferred income tax consequences of the intra-entity transfer to be recorded when the transaction occurs. The exception to defer the tax consequences of inventory transactions is maintained. These changes became effective for Arconic on January 1, 2017. Management has determined that the adoption of this guidance did not have a material impact on the Consolidated Financial Statements. In January 2017, the FASB issued changes to the subsequent measurement of goodwill by eliminating step 2 from the goodwill impairment test, which previously required measurement of any goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. An entity will perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value without exceeding the total amount of goodwill allocated to that reporting unit. Arconic has elected to early adopt this guidance as of January 1, 2017 and will apply it on a prospective basis. Management does not anticipate that the adoption of these changes will have a material impact on the Consolidated Financial Statements. In January 2017, the FASB issued changes which narrow the definition of a business and require an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets, which would not constitute the acquisition of a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs. Arconic has elected to early adopt this guidance as of January 1, 2017 and will apply it on a prospective basis. Management does not anticipate that the adoption of these changes will have a material impact on the Consolidated Financial Statements. Issued In May 2014, the FASB issued changes to the recognition of revenue from contracts with customers. These changes created a comprehensive framework for all entities in all industries to apply in the determination of when to recognize revenue and, therefore, supersede virtually all existing revenue recognition requirements and guidance. This framework is expected to result in less complex guidance in application while providing a consistent and comparable methodology for revenue recognition. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this principle, an entity should apply the following steps: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract(s), (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract(s), and (v) recognize revenue when, or as, the entity satisfies a performance obligation. In August 2015, the FASB deferred the effective date of the new guidance by one year, making these changes effective for Arconic on January 1, 2018. The Company has formed a project assessment and adoption team and is currently reviewing contract terms and assessing the impact of adopting the new guidance on the Consolidated Financial Statements. An estimate of the impact of this standard is not currently determinable. In January 2016, the FASB issued changes to equity investments. These changes require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. Additionally, the impairment assessment of equity investments without readily determinable fair values has been simplified by requiring a qualitative assessment to identify impairment. These changes become effective for Arconic on January 1, 2018. Management has determined that the potential impact of these changes on the Consolidated Financial Statements will not be material. In February 2016, the FASB issued changes to the accounting and presentation of leases. These changes require lessees to recognize a right of use asset and lease liability on the balance sheet for all leases with terms longer than 12 months. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize a right of use asset and lease liability. Additionally, when measuring assets and liabilities arising from a lease, optional payments should be included only if the lessee is reasonably certain to exercise an option to extend the lease, exercise a purchase option, or not exercise an option to terminate the lease. These changes become effective for Arconic on January 1, 2019. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. An estimate of the impact of this standard is not currently determinable. In June 2016, the FASB added a new impairment model (known as the current expected credit loss (CECL) model) that is based on expected losses rather than incurred losses. Under the new guidance, an entity recognizes as an allowance 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. The CECL model does not have a minimum threshold for recognition of impairment losses and entities will need to measure expected credit losses on assets that have a low risk of loss. These changes become effective for Arconic on January 1, 2020. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. In August 2016, the FASB issued changes to the classification of certain cash receipts and cash payments within the statement of cash flows. The guidance identifies eight specific cash flow items and the sections where they must be presented within the statement of cash flows. These changes become effective for Arconic on January 1, 2018 and early adoption is permitted. Management does not expect these changes to have a material impact on the Consolidated Financial Statements. In November 2016, the FASB issued changes to the classification of cash and cash equivalents within the cash flow statement. Restricted cash and restricted cash equivalents will be included within the cash and cash equivalents line on the cash flow statement and a reconciliation must be prepared to the statement of financial position. Transfers between restricted cash and restricted cash equivalents and cash and cash equivalents will no longer be presented as cash flow activities in the statement of cash flows and material balances of restricted cash and restricted cash equivalents must disclose information regarding the nature of the restrictions. These changes become effective for Arconic on January 1, 2018. Management has determined that the adoption of these changes will not have a material impact on the Consolidated Financial Statements. In March 2017, the FASB issued changes to shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. These changes become effective for Arconic on January 1, 2019 and early adoption is permitted. Management has determined that the adoption of these changes will not have a material impact on the Consolidated Financial Statements. In March 2017, the FASB issued changes to the presentation of net periodic pension cost and net periodic postretirement benefit cost. The new guidance requires registrants to present the service cost component of net periodic benefit cost in the same income statement line item or items as other employee compensation costs arising from services rendered during the period. In addition, only the service cost component will be eligible for asset capitalization. Registrants will present the other components of net periodic benefit cost separately from the service cost component; and, the line item or items used in the income statement to present the other components of net periodic benefit cost must be disclosed. These changes become effective for Arconic on January 1, 2018, including interim periods within those fiscal years. Early adoption is permitted as of the beginning of an annual period. The new standard must be adopted retrospectively for the presentation of the service cost component and the other components of net periodic benefit cost in the income statement, and prospectively for the asset capitalization of the service cost component of net periodic benefit cost. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements.

B. Recently Adopted and Recently Issued Accounting Guidance

Adopted

In March 2016, the Financial Accounting Standards Board (“FASB”) issued changes to employee share-based payment accounting. Previously, an entity determined for each share-based payment award whether the difference between the deduction for tax purposes and the compensation cost recognized for financial reporting purposes resulted in either an excess tax benefit or a tax deficiency. Excess tax benefits were recognized in additional paid-in capital; tax deficiencies were recognized either as an offset to accumulated excess tax benefits, if any, or in the income statement. Excess tax benefits were not recognized until the deduction reduced taxes payable. The changes require all excess tax benefits and tax deficiencies related to share-based payment awards to be recognized as income tax expense or benefit in the income statement. The tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur. An entity also should recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. Additionally, the presentation of excess tax benefits related to share-based payment awards in the statement of cash flows changed. Previously, excess tax benefits were separated from other income tax cash flows and classified as a financing activity. The changes require excess tax benefits to be classified along with other income tax cash flows as an operating activity. Also, the changes require cash paid by an employer when directly withholding shares for tax-withholding purposes to be classified as a financing activity. Additionally, for a share-based award to qualify for equity classification it previously could not be partially settled in cash in excess of the employer’s minimum statutory withholding requirements. The changes permit equity classification of share-based awards for withholdings up to the maximum statutory tax rates in applicable jurisdictions. These changes became effective for Arconic on January 1, 2017. Management has concluded that the adoption of this guidance did not have a material effect on the Consolidated Financial Statements.

In March 2016, the FASB issued changes eliminating the requirement for an investor to adjust an equity method investment, results of operations, and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held as a result of an increase in the level of ownership interest or degree of influence. Additionally, an entity that has an available-for-sale equity security that becomes qualified for the equity method of accounting must recognize through earnings the unrealized holding gain or loss in accumulated other comprehensive income at the date the investment becomes qualified for use of the equity method. These changes became effective for Arconic on January 1, 2017. Management has concluded that the adoption of this guidance did not have a material impact on the Consolidated Financial Statements.

In March 2016, the FASB issued changes to derivative instruments designated as hedging instruments. These changes clarify that a change in the counterparty to a derivative instrument that has been designated as a hedging instrument does not, in and of itself, require dedesignation of that hedging relationship provided that all other hedge accounting criteria continue to be met. These changes became effective for Arconic on January 1, 2017. Management has determined that the adoption of this guidance did not have a material impact on the Consolidated Financial Statements.

In October 2016, the FASB issued changes to the accounting for Intra-Entity transactions, other than inventory. Previously, no immediate tax impact was recognized in the consolidated financial statements as a result of intra-entity transfers of assets. The previous standard precluded an entity from reflecting a tax benefit or expense from an intra-entity transfer between entities that file separate tax returns, whether or not such entities were in different tax jurisdictions, until the asset was sold to a third party or otherwise recovered. The previous standard also prohibited recognition by the buyer of a deferred tax asset for the temporary difference arising from the excess of the buyer’s tax basis over the cost to the seller. The changes require the current and deferred income tax consequences of the intra-entity transfer to be recorded when the transaction occurs. The exception to defer the tax consequences of inventory transactions is maintained. These changes became effective for Arconic on January 1, 2017. Management has determined that the adoption of this guidance did not have a material impact on the Consolidated Financial Statements.

In January 2017, the FASB issued changes to the subsequent measurement of goodwill by eliminating step 2 from the goodwill impairment test, which previously required measurement of any goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. An entity will perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value without exceeding the total amount of goodwill allocated to that reporting unit. Arconic has elected to early adopt this guidance as of January 1, 2017 and will apply it on a prospective basis. Management does not anticipate that the adoption of these changes will have a material impact on the Consolidated Financial Statements.

In January 2017, the FASB issued changes which narrow the definition of a business and require an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets, which would not constitute the acquisition of a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs. Arconic has elected to early adopt this guidance as of January 1, 2017 and will apply it on a prospective basis. Management does not anticipate that the adoption of these changes will have a material impact on the Consolidated Financial Statements.

Issued

In May 2014, the FASB issued changes to the recognition of revenue from contracts with customers. These changes created a comprehensive framework for all entities in all industries to apply in the determination of when to recognize revenue and, therefore, supersede virtually all existing revenue recognition requirements and guidance. This framework is expected to result in less complex guidance in application while providing a consistent and comparable methodology for revenue recognition. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this principle, an entity should apply the following steps: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract(s), (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract(s), and (v) recognize revenue when, or as, the entity satisfies a performance obligation. In August 2015, the FASB deferred the effective date of the new guidance by one year, making these changes effective for Arconic on January 1, 2018. The Company has formed a project assessment and adoption team and is currently reviewing contract terms and assessing the impact of adopting the new guidance on the Consolidated Financial Statements. An estimate of the impact of this standard is not currently determinable.

In January 2016, the FASB issued changes to equity investments. These changes require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. Additionally, the impairment assessment of equity investments without readily determinable fair values has been simplified by requiring a qualitative assessment to identify impairment. These changes become effective for Arconic on January 1, 2018. Management has determined that the potential impact of these changes on the Consolidated Financial Statements will not be material.

In February 2016, the FASB issued changes to the accounting and presentation of leases. These changes require lessees to recognize a right of use asset and lease liability on the balance sheet for all leases with terms longer than 12 months. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize a right of use asset and lease liability. Additionally, when measuring assets and liabilities arising from a lease, optional payments should be included only if the lessee is reasonably certain to exercise an option to extend the lease, exercise a purchase option, or not exercise an option to terminate the lease. These changes become effective for Arconic on January 1, 2019. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. An estimate of the impact of this standard is not currently determinable.

In June 2016, the FASB added a new impairment model (known as the current expected credit loss (CECL) model) that is based on expected losses rather than incurred losses. Under the new guidance, an entity recognizes as an allowance 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. The CECL model does not have a minimum threshold for recognition of impairment losses and entities will need to measure expected credit losses on assets that have a low risk of loss. These changes become effective for Arconic on January 1, 2020. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements.

In August 2016, the FASB issued changes to the classification of certain cash receipts and cash payments within the statement of cash flows. The guidance identifies eight specific cash flow items and the sections where they must be presented within the statement of cash flows. These changes become effective for Arconic on January 1, 2018 and early adoption is permitted. Management does not expect these changes to have a material impact on the Consolidated Financial Statements.

In November 2016, the FASB issued changes to the classification of cash and cash equivalents within the cash flow statement. Restricted cash and restricted cash equivalents will be included within the cash and cash equivalents line on the cash flow statement and a reconciliation must be prepared to the statement of financial position. Transfers between restricted cash and restricted cash equivalents and cash and cash equivalents will no longer be presented as cash flow activities in the statement of cash flows and material balances of restricted cash and restricted cash equivalents must disclose information regarding the nature of the restrictions. These changes become effective for Arconic on January 1, 2018. Management has determined that the adoption of these changes will not have a material impact on the Consolidated Financial Statements.

In March 2017, the FASB issued changes to shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. These changes become effective for Arconic on January 1, 2019 and early adoption is permitted. Management has determined that the adoption of these changes will not have a material impact on the Consolidated Financial Statements.

In March 2017, the FASB issued changes to the presentation of net periodic pension cost and net periodic postretirement benefit cost. The new guidance requires registrants to present the service cost component of net periodic benefit cost in the same income statement line item or items as other employee compensation costs arising from services rendered during the period. In addition, only the service cost component will be eligible for asset capitalization. Registrants will present the other components of net periodic benefit cost separately from the service cost component; and, the line item or items used in the income statement to present the other components of net periodic benefit cost must be disclosed. These changes become effective for Arconic on January 1, 2018, including interim periods within those fiscal years. Early adoption is permitted as of the beginning of an annual period. The new standard must be adopted retrospectively for the presentation of the service cost component and the other components of net periodic benefit cost in the income statement, and prospectively for the asset capitalization of the service cost component of net periodic benefit cost. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements.