Subsequent Events	12 Months Ended
Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Management evaluated all activity of Arconic and concluded that no subsequent events have occurred that would require recognition in the Consolidated Financial Statements or disclosure in the Notes to the Consolidated Financial Statements, except as noted below: On January 22, 2019, the Company announced that its Board of Directors (the Board) had determined to no longer pursue a potential sale of Arconic as part of its strategy and portfolio review. On February 6, 2019, the Company announced that the Board appointed John C. Plant, current Chairman of the Board, as Chairman and Chief Executive Officer of the Company, effective February 6, 2019, to succeed Chip Blankenship, who ceased to serve as Chief Executive Officer of the Company and resigned as a member of the Board, in each case as of that date. In addition, the Company announced that the Board appointed Elmer L. Doty, current member of the Board, as President and Chief Operating Officer, a newly created position, effective February 6, 2019. Mr. Doty will remain a member of the Board. The Company also announced that Arthur D. Collins, Jr., current member of the Board, has been appointed interim Lead Independent Director of the Company, effective February 6, 2019. On February 8, 2019, the Company announced the following key initiatives as part of its ongoing strategy and portfolio review: plans to reduce operating costs, designed to maximize the impact in 2019; the planned separation of its portfolio into Engineered Products and Forgings (EP&F) and Global Rolled Products (GRP), with a spin-off of one of the businesses; the potential sale of businesses that do not best fit into EP&F or GRP; execute its previously authorized $500 share repurchase program in the first half of 2019; the Board authorized an additional $500 of share repurchases, effective through the end of 2020; and plans to reduce its quarterly common stock dividend from $0.06 to $0.02 per share. On February 19, 2019, the Company entered into an accelerated share repurchase (“ASR”) agreement with JPMorgan Chase Bank to repurchase $700 of its common stock, pursuant to the share repurchase program previously authorized by the Board. Under the ASR agreement, Arconic will receive initial delivery of approximately 32 million shares on February 21, 2019. The final number of shares to be repurchased will be based on the volume-weighted average price of Arconic’s common stock during the term of the transaction, less a discount. The ASR agreement is expected to be completed during the first half of 2019. The Company will evaluate its organizational structure in conjunction with the planned separation of its portfolio and changes to its reportable segments are expected in the first half of 2019.

Subsequent Events

Management evaluated all activity of Arconic and concluded that no subsequent events have occurred that would require recognition in the Consolidated Financial Statements or disclosure in the Notes to the Consolidated Financial Statements, except as noted below:

On January 22, 2019, the Company announced that its Board of Directors (the Board) had determined to no longer pursue a potential sale of Arconic as part of its strategy and portfolio review.

On February 6, 2019, the Company announced that the Board appointed John C. Plant, current Chairman of the Board, as Chairman and Chief Executive Officer of the Company, effective February 6, 2019, to succeed Chip Blankenship, who ceased to serve as Chief Executive Officer of the Company and resigned as a member of the Board, in each case as of that date. In addition, the Company announced that the Board appointed Elmer L. Doty, current member of the Board, as President and Chief Operating Officer, a newly created position, effective February 6, 2019. Mr. Doty will remain a member of the Board. The Company also announced that Arthur D. Collins, Jr., current member of the Board, has been appointed interim Lead Independent Director of the Company, effective February 6, 2019.

On February 8, 2019, the Company announced the following key initiatives as part of its ongoing strategy and portfolio review: plans to reduce operating costs, designed to maximize the impact in 2019; the planned separation of its portfolio into Engineered Products and Forgings (EP&F) and Global Rolled Products (GRP), with a spin-off of one of the businesses; the potential sale of businesses that do not best fit into EP&F or GRP; execute its previously authorized $500 share repurchase program in the first half of 2019; the Board authorized an additional $500 of share repurchases, effective through the end of 2020; and plans to reduce its quarterly common stock dividend from $0.06 to $0.02 per share.

On February 19, 2019, the Company entered into an accelerated share repurchase (“ASR”) agreement with JPMorgan Chase Bank to repurchase $700 of its common stock, pursuant to the share repurchase program previously authorized by the Board. Under the ASR agreement, Arconic will receive initial delivery of approximately 32 million shares on February 21, 2019. The final number of shares to be repurchased will be based on the volume-weighted average price of Arconic’s common stock during the term of the transaction, less a discount. The ASR agreement is expected to be completed during the first half of 2019.

The Company will evaluate its organizational structure in conjunction with the planned separation of its portfolio and changes to its reportable segments are expected in the first half of 2019.