v3.20.1

Acquisitions and Divestitures (Details) $ in Millions			3 Months Ended			12 Months Ended
	Mar. 01, 2020 USD ($) employee	Feb. 01, 2020 USD ($) employee	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Sales			$ 1,611		$ 1,841
Disposed of by sale | Aluminum Rolling Mill in Itapissuma, Brazil
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration received		$ 46
Gain (loss) on sale		$ (59)
Sale transaction costs			6	$ 53
Total Sales						$ 143	$ 179	$ 162
Number of employees | employee		500
Disposed of by sale | Hard Alloy Extrusions Plant in South Korea
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration received	$ 55
Gain (loss) on sale	31		$ (31)
Write-off of goodwill	$ 6
Total Sales						$ 51	$ 53	$ 50
Number of employees | employee	160

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