Restructuring and Other Charges, Net (2022 Actions) - Additional Information (Detail) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($)	Dec. 31, 2024 USD ($) Employees	Dec. 31, 2023 USD ($) Employees	Dec. 31, 2022 USD ($) Employees
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net		$ 341	$ 184	$ 696
Number of employees under defined benefit plan | Employees			530	4,400
Magnesium Smelter Facility in Addy [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ 29			$ 29
San Ciprian Facility [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			$ 53
Legal Disputes Related to 2019 Divestiture [Member] | Avilés and La Coruña Facilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				79
Asset Impairment [Member] | MRN [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				58
Valuation Allowance on Brazil Value-Added Taxes [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				83
Demolition Obligations and Environmental Remediation at Previously Closed Sites [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				34
Additional Contract Costs [Member] | Wenatchee (Washington) and Intalco (Washington) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				7
Additional Environmental and Asset Retirement [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				26
Group Annuity Contract [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			21	635
Pension Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			$ 235	1,000
Number of employees under defined benefit plan | Employees		16,000
2022 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				$ 696