Long-Lived Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation and amortization	$ 7,070	$ 6,769
Properties, plants and equipment excluding construction work in progress	4,636	4,965
Construction work-in-progress	741	739
Properties, plants, and equipment, net	5,377	5,704
Land and land rights
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	133	136
Structures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,349	2,364
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,224	9,234
Depreciable property, plant and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,706	$ 11,734
Arconic Engines
Property, Plant and Equipment [Line Items]
Asset impairment charges	428
Property, Plant and Equipment \| Arconic Engines
Property, Plant and Equipment [Line Items]
Asset impairment charges	198
Indefinite-lived Intangible Assets
Property, Plant and Equipment [Line Items]
Asset impairment charges	197
Other Noncurrent Assets \| Arconic Engines
Property, Plant and Equipment [Line Items]
Asset impairment charges	$ 33

Properties plants and equipment excluding construction work in progress.

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Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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