Restructuring and Other Charges, Net - Schedule of Restructuring and Other Charges, Net by Reportable Segments, Pretax (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ 202	$ 149
Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	197	147
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	5	2
Alumina [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ 197	1
Aluminum Segment [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net		$ 146