Property, Plants, and Equipment, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation and amortization	$ 6,778	$ 6,392
Properties, plants, and equipment, net	5,645	5,594
Undiscounted cash flows, effect of one percentage point decrease on net cash flows	$ 6
Disks Business
Property, Plant and Equipment [Line Items]
Estimated undiscounted cash flows in excess its carrying value, percent	13.00%
Arconic Engines
Property, Plant and Equipment [Line Items]
Long-lived assets	$ 515
Land and land rights
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	138	140
Structures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,374	2,395
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,244	8,830
Depreciable property, plant and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,756	11,365
Properties, plants, and equipment, net	4,978	4,973
Construction work-in-progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 667	$ 621