Long-Lived Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation and amortization	$ 7,013	$ 6,769
Properties, plants and equipment excluding construction work in progress	4,750	4,965
Construction work-in-progress	767	739
Properties, plants, and equipment, net	5,517	5,704
Land and land rights
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	136	136
Structures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,378	2,364
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,249	9,234
Depreciable property, plant and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,763	$ 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