Arconic Inc Separation Transaction and Discontinued Operations - Summary of Results of Discontinued Operations (Details) - Arconic Corportion - Discontinued Operations, Disposed of by Means Other than Sale - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales	$ 1,575	$ 7,094
Cost of goods sold	1,293	6,013
Selling, general administrative, research and development and other expenses	106	346
Provision for depreciation and amortization	58	241
Restructuring and other (credits) charges	(18)	38
Operating income from discontinued operations	136	456
Interest expense, net	7	0
Other expense, net	41	91
Income from discontinued operations	88	365
Provision for income taxes	38	21
Income from discontinued operations after income taxes	$ 50	$ 344