Acquisitions and Divestitures	3 Months Ended
Mar. 31, 2019
Business Combinations [Abstract]
Acquisitions and Divestitures	Acquisitions and Divestitures 2018 Divestitures. On April 2, 2018, Arconic completed the sale of its Latin America extrusions business to a subsidiary of Hydro Extruded Solutions AS for $2 following the settlement of post-closing and other adjustments in December 2018. As a result of entering into the agreement to sell the Latin America extrusions business in December 2017, a charge of $41 was recognized in the fourth quarter of 2017 in Restructuring and other charges in the Statement of Consolidated Operations related to the non-cash impairment of the net book value of the business and an additional charge of $2 related to a post-closing adjustment was recognized in the fourth quarter of 2018. The operating results and assets and liabilities of the business were included in the Transportation and Construction Solutions segment. This business generated sales of $25 in the first quarter of 2018 and had 612 employees at the time of divestiture. On July 31, 2018, the Company announced that it had initiated a sale process of its Building and Construction Systems (BCS) business, as part of the Company’s ongoing strategy and portfolio review. In the first quarter of 2019, the Company decided to no longer pursue the sale of BCS and the business continues to be reported in the Transportation and Construction Solutions segment. On October 31, 2018, the Company sold its Texarkana, Texas rolling mill and cast house, which had a combined net book value of $63, to Ta Chen International, Inc. for $302 in cash, including the settlement of post-closing adjustments, plus additional contingent consideration of up to $50. The contingent consideration relates to the achievement of various milestones within 36 months of the transaction closing date associated with operationalizing the rolling mill equipment. The operating results and assets and liabilities of the business were included in the Global Rolled Products segment. The Texarkana rolling mill facility had previously been idle since late 2009. In early 2016, the Company restarted the Texarkana cast house to meet demand for aluminum slab. As part of the agreement, the Company will continue to produce aluminum slab at the facility for a period of 18 months through a lease back of the cast house building and equipment, after which time, Ta Chen will perform toll processing of metal for the Company for a period of six months. The Company will supply Ta Chen with cold-rolled aluminum coil during this 24-month period. The sale of the rolling mill and cast house has been accounted for separately. The gain on the sale of the rolling mill of $154, including the fair value of contingent consideration of $5, was recorded in Restructuring and other charges in the Statement of Consolidated Operations in the fourth quarter of 2018. The Company will reevaluate its estimate of the remaining $45 of contingent consideration to which it will be entitled at the end of each reporting period and recognize any changes thereto in the Statement of Consolidated Operations. The Company has continuing involvement related to the lease back of the cast house. As a result, in 2018, the Company continued to treat the cast house building and equipment that it sold to Ta Chen as owned and therefore reflected the following balances in its Consolidated Balance Sheet at December 31, 2018: assets of $24 in Properties, plants, and equipment, net; cash proceeds of $119 in Other noncurrent liabilities and deferred credits (which included a deferred gain of $95); and a deferred tax asset of $22 in Other noncurrent assets. In the first quarter of 2019, in conjunction with the adoption of the new lease accounting standard (see Note B), the Company's continuing involvement no longer requires deferral of the recognition of the cast house sale. As such, the cash proceeds, fixed assets, and deferred tax asset related to the cast house were reclassified to Accumulated deficit as a cumulative effect of an accounting change.

Acquisitions and Divestitures

2018 Divestitures. On April 2, 2018, Arconic completed the sale of its Latin America extrusions business to a subsidiary of Hydro Extruded Solutions AS for $2 following the settlement of post-closing and other adjustments in December 2018. As a result of entering into the agreement to sell the Latin America extrusions business in December 2017, a charge of $41 was recognized in the fourth quarter of 2017 in Restructuring and other charges in the Statement of Consolidated Operations related to the non-cash impairment of the net book value of the business and an additional charge of $2 related to a post-closing adjustment was recognized in the fourth quarter of 2018. The operating results and assets and liabilities of the business were included in the Transportation and Construction Solutions segment. This business generated sales of $25 in the first quarter of 2018 and had 612 employees at the time of divestiture.

On July 31, 2018, the Company announced that it had initiated a sale process of its Building and Construction Systems (BCS) business, as part of the Company’s ongoing strategy and portfolio review. In the first quarter of 2019, the Company decided to no longer pursue the sale of BCS and the business continues to be reported in the Transportation and Construction Solutions segment.

On October 31, 2018, the Company sold its Texarkana, Texas rolling mill and cast house, which had a combined net book value of $63, to Ta Chen International, Inc. for $302 in cash, including the settlement of post-closing adjustments, plus additional contingent consideration of up to $50. The contingent consideration relates to the achievement of various milestones within 36 months of the transaction closing date associated with operationalizing the rolling mill equipment. The operating results and assets and liabilities of the business were included in the Global Rolled Products segment. The Texarkana rolling mill facility had previously been idle since late 2009. In early 2016, the Company restarted the Texarkana cast house to meet demand for aluminum slab. As part of the agreement, the Company will continue to produce aluminum slab at the facility for a period of 18 months through a lease back of the cast house building and equipment, after which time, Ta Chen will perform toll processing of metal for the Company for a period of six months. The Company will supply Ta Chen with cold-rolled aluminum coil during this 24-month period.

The sale of the rolling mill and cast house has been accounted for separately. The gain on the sale of the rolling mill of $154, including the fair value of contingent consideration of $5, was recorded in Restructuring and other charges in the Statement of Consolidated Operations in the fourth quarter of 2018. The Company will reevaluate its estimate of the remaining $45 of contingent consideration to which it will be entitled at the end of each reporting period and recognize any changes thereto in the Statement of Consolidated Operations.

The Company has continuing involvement related to the lease back of the cast house. As a result, in 2018, the Company continued to treat the cast house building and equipment that it sold to Ta Chen as owned and therefore reflected the following balances in its Consolidated Balance Sheet at December 31, 2018: assets of $24 in Properties, plants, and equipment, net; cash proceeds of $119 in Other noncurrent liabilities and deferred credits (which included a deferred gain of $95); and a deferred tax asset of $22 in Other noncurrent assets. In the first quarter of 2019, in conjunction with the adoption of the new lease accounting standard (see Note B), the Company's continuing involvement no longer requires deferral of the recognition of the cast house sale. As such, the cash proceeds, fixed assets, and deferred tax asset related to the cast house were reclassified to Accumulated deficit as a cumulative effect of an accounting change.