Restructuring and Other Charges - Restructuring and Other Charges by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)	$ 14	$ 3	$ 612	$ 61
Operating segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)	3	0	6	(6)
Operating segments | Rolled Products
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)	0	(1)	(1)	15
Operating segments | Building and Construction Systems
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)	0	0	(1)	6
Operating segments | Extrusions
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)	3	(1)	6	27
Corporate, Non-Segment
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)	$ 11	$ 3	$ 606	$ 67