Segment and Related Information - Schedule of Third-party Sales by Product Division (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation Of Revenue [Line Items]
Sales	$ 10,551	$ 12,451	$ 12,152
Primary Aluminum [Member]
Disaggregation Of Revenue [Line Items]
Sales	7,045	8,887	8,420
Alumina [Member]
Disaggregation Of Revenue [Line Items]
Sales	3,103	3,478	3,125
Flat-Rolled Aluminum [Member]
Disaggregation Of Revenue [Line Items]
Sales			320
Energy [Member]
Disaggregation Of Revenue [Line Items]
Sales	118	201	286
Bauxite [Member]
Disaggregation Of Revenue [Line Items]
Sales	466	168	207
Other Products [Member]
Disaggregation Of Revenue [Line Items]
Sales	$ (181)	$ (283)	$ (206)