v3.20.2

Acquisitions and Divestitures (Details) $ in Millions			3 Months Ended					9 Months Ended		12 Months Ended
	Mar. 01, 2020 USD ($) employee	Feb. 01, 2020 USD ($) employee	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 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			$ 1,415				$ 1,805	$ 4,213	$ 5,569
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)
Total Sales										$ 143	$ 179	$ 162
Number of employees | employee		500
Asset Impairment Charges					$ 6	$ 6	$ 59			53
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			$ 1
Write-off of goodwill	$ 6
Total Sales										$ 51	$ 53	$ 50
Number of employees | employee	160

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