Arconic Inc. Separation Transaction and Discontinued Operations - Summary of Results of Discontinued Operations (Details) - Arconic Corporation - Discontinued Operations, Disposed of by Means Other than Sale - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Restructuring Cost and Reserve [Line Items]
Sales		$ 1,575
Cost of goods sold		1,293
Selling, general administrative, research and development and other expenses		106
Provision for depreciation and amortization		58
Restructuring and other charges		(18)
Operating income from discontinued operations		136
Interest expense, net		7
Other expense, net		41
Income from discontinued operations		88
Provision for income taxes		38
Income from discontinued operations after income taxes	$ 0	$ 50