Investments - Summary of Balance Sheet Information for Alcoa Corporation's Equity Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Current assets	$ 4,405	$ 5,250
Current liabilities	3,030	3,004
Ma'aden Joint Venture [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Current assets	1,433	1,769
Noncurrent assets	6,958	6,993
Current liabilities	1,444	1,255
Noncurrent liabilities	4,272	4,314
Mining [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Current assets	8	5
Noncurrent assets	419	363
Current liabilities	5	3
Noncurrent liabilities	24	24
Energy [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Current assets	103	114
Noncurrent assets	310	301
Current liabilities	16	13
Noncurrent liabilities	34	26
Other [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Current assets	181	134
Noncurrent assets	764	757
Current liabilities	89	114
Noncurrent liabilities	$ 117	$ 84