Arconic Inc Separation Transaction and Discontinued Operations - Narrative (Details)					3 Months Ended	6 Months Ended	12 Months Ended
	Apr. 01, 2020 company	Mar. 25, 2020 USD ($)	Feb. 01, 2020 USD ($)	Oct. 31, 2018 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Feb. 07, 2020 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of independent, publicly-traded companies resulting from proposed separation transaction | company	2
Debt issuance costs (C and R)							$ 11,000,000	$ 61,000,000	$ 0
Asset impairment charges							$ 15,000,000	5,000,000	442,000,000
Aluminum Rolling Mill
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration			$ 50,000,000
Gain (loss) on disposition of business, before tax			$ (59,000,000)
Asset impairment charges					$ 6,000,000	$ 53,000,000		6,000,000
Hard Alloy Extrusions Plant In South Korea
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration					62,000,000			62,000,000
Texarkana, Texas Rolling Mill And Cast House
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposition of business, before tax									$ 20,000,000
Period of operationalizing rolling mill equipment of transaction closing date				36 months
Texarkana, Texas Rolling Mill And Cast House | Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Additional contingent consideration				$ 50,000,000
Lien Notes
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt issuance costs (C and R)					$ 45,000,000			$ 45,000,000
Senior Notes | Second-Lien Notes Due 2028
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Aggregate principal amount										$ 600,000,000
Convertible notes, interest rate percentage										6.125%
Line of Credit | Senior Secured First Lien Term B Loan Facility Due 2027 | Secured Debt
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Aggregate principal amount		$ 600,000,000
Debt instrument, term		7 years