v3.20.2

Restructuring and Other Charges - Narrative (Details) $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 01, 2020 USD ($)	Jun. 30, 2020 USD ($) employee claimants	Jun. 30, 2019 USD ($) employee	Jun. 30, 2020 USD ($) employee	Jun. 30, 2019 USD ($) employee	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 77	$ 38	$ 58	$ 40
Restructuring and other charges		$ 77	38	58	40
Number of employees separated | employee		410
Cash payments, restructuring				$ 13			$ 15
Forecast
Restructuring Cost and Reserve [Line Items]
Cash payments, restructuring						$ 7
2020 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Expected number of employees separated | employee				550
Number of employees separated | employee				150
2019 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Expected number of employees separated | employee				380
Number of employees separated | employee				320
2019 Restructuring Program [Member] | Previously Reported [Member]
Restructuring Cost and Reserve [Line Items]
Expected number of employees separated | employee				480
Layoff costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 17
Cash payments, restructuring				$ 11			12
Layoff costs | 2020 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Cash payments, restructuring		5
Layoff costs | 2019 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Cash payments, restructuring		2		6
Allocated costs, ParentCo
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		0	$ 12	2	3
Other miscellaneous costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		2		4	2
Cash payments, restructuring				$ 2			$ 3
Pension Settlement Cost [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		55
Reversal of Reserve [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		12
Environmental [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		5
Legacy Non-Income Taxes [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		4
Impairment of Carrying Value of Tradename [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					$ 10
Hard Alloy Extrusions Plant in South Korea | Disposed of by sale
Restructuring Cost and Reserve [Line Items]
Gain (loss) on sale	$ 31	1
Rolled Products and Building and Construction Systems
Restructuring Cost and Reserve [Line Items]
Number of employees separated | employee			95		250
Rolled Products and Building and Construction Systems | Layoff costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 14		$ 25
Building and Construction System and Extrustions [Member] | Layoff costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 8
Number of employees separated | claimants		140
Building and Construction System and Extrustions [Member] | Other miscellaneous costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 11

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