Basis of Presentation	3 Months Ended
Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The interim Consolidated Financial Statements of Arconic Inc. 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 2017 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, 2017, which includes all disclosures required by GAAP. Certain amounts in previously issued financial statements were reclassified to conform to the current period presentation (see below). On January 1, 2018, Arconic adopted new guidance issued by the Financial Accounting Standards Board (FASB) related to the following: presentation of net periodic pension cost and net periodic postretirement benefit cost that required a reclassification of costs within the Statement of Consolidated Operations; presentation of certain cash receipts and cash payments within the Statement of Consolidated Cash Flows that required a reclassification of amounts between operating and either financing or investing activities; and the classification of restricted cash within the statement of cash flows. See Note B for further details. In January 2018, management changed the organizational structure of the businesses in its Engineered Products and Solutions (EP&S) segment, from four business units to three business units, with a focus on aligning its internal structure to core markets and customers and reducing cost. As a result of this change in the EP&S segment organizational structure, management assessed and concluded that each of the three business units represent reporting units for goodwill impairment evaluation purposes. Also, as a result of the reorganization, goodwill was reallocated to the three new reporting units and evaluated for impairment during the first quarter of 2018. The fair value of each reporting unit exceeded its carrying value; thus there was no goodwill impairment. More than 92% of Arconic’s total goodwill at March 31, 2018 was allocated to the following three EP&S reporting units: Arconic Engines ($2,095), Arconic Fastening Systems ($1,623) and Arconic Engineered Structures ($517).

Basis of Presentation

The interim Consolidated Financial Statements of Arconic Inc. 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 2017 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, 2017, which includes all disclosures required by GAAP. Certain amounts in previously issued financial statements were reclassified to conform to the current period presentation (see below).

On January 1, 2018, Arconic adopted new guidance issued by the Financial Accounting Standards Board (FASB) related to the following: presentation of net periodic pension cost and net periodic postretirement benefit cost that required a reclassification of costs within the Statement of Consolidated Operations; presentation of certain cash receipts and cash payments within the Statement of Consolidated Cash Flows that required a reclassification of amounts between operating and either financing or investing activities; and the classification of restricted cash within the statement of cash flows. See Note B for further details.

In January 2018, management changed the organizational structure of the businesses in its Engineered Products and Solutions (EP&S) segment, from four business units to three business units, with a focus on aligning its internal structure to core markets and customers and reducing cost. As a result of this change in the EP&S segment organizational structure, management assessed and concluded that each of the three business units represent reporting units for goodwill impairment evaluation purposes. Also, as a result of the reorganization, goodwill was reallocated to the three new reporting units and evaluated for impairment during the first quarter of 2018. The fair value of each reporting unit exceeded its carrying value; thus there was no goodwill impairment. More than 92% of Arconic’s total goodwill at March 31, 2018 was allocated to the following three EP&S reporting units: Arconic Engines ($2,095), Arconic Fastening Systems ($1,623) and Arconic Engineered Structures ($517).