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Financial contributions.

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Payment amount refund percentage.

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Tax credit previously claimed and disallowed by tax authority.

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Carrying amount as of the balance sheet date of unearned revenue or income, not otherwise specified in the taxonomy, which is expected to be taken into income after one year or beyond the normal operating cycle, if longer and noncurrent obligations not separately disclosed in the balance sheet (other liabilities, noncurrent).

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A credit or adjustment for government or taxing authority authorized decrease in taxes owed as a result of meeting certain tax policy conditions.

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Contingencies and Commitments - Additional Information - 1 (Detail) $ in Millions					1 Months Ended															3 Months Ended	6 Months Ended	12 Months Ended
	Oct. 15, 2024 USD ($)	Jul. 18, 2024 USD ($)	Sep. 17, 2020 USD ($)	Sep. 17, 2020 AUD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2024 BRL (R$)	Sep. 30, 2024 USD ($)	Sep. 30, 2024 BRL (R$)	Aug. 31, 2022 USD ($)	Aug. 31, 2022 BRL (R$)	Jul. 31, 2022 USD ($)	Jul. 31, 2022 BRL (R$)	Mar. 31, 2022 USD ($)	Mar. 31, 2022 BRL (R$)	Feb. 28, 2022 USD ($)	Feb. 28, 2022 BRL (R$)	Mar. 31, 2013 USD ($)	May 31, 2012 USD ($)	May 31, 2012 BRL (R$)	Sep. 30, 2020 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2024 BRL (R$)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2012 BRL (R$)	Dec. 31, 2024 AUD ($)	Jul. 31, 2024	Dec. 31, 2023 AUD ($)	Jul. 31, 2022 BRL (R$)	Feb. 28, 2022 BRL (R$)	Sep. 30, 2020 AUD ($)	Jul. 07, 2020 USD ($)	Jul. 07, 2020 AUD ($)	Mar. 31, 2013 BRL (R$)	Dec. 31, 2012 BRL (R$)
Loss Contingencies [Line Items]
Other noncurrent liabilities and deferred credits (U)					$ 656,000,000																$ 568,000,000	$ 656,000,000		$ 568,000,000
Restructuring and other charges, net (D)																						341,000,000		184,000,000	$ 696,000,000
Payment for settlements to former employees	$ 5,000,000	$ 5,000,000																			76,000,000
Australian Taxation Office [Member] \| Foreign Jurisdiction [Member] \| AofA [Member]
Loss Contingencies [Line Items]
Additional income tax payable, exclusive of interest and penalties																																			$ 132,000,000	$ 214
Notices include claims for compounded interest on the tax amount																																			$ 438,000,000	$ 707
Proposed administrative penalties			$ 79,000,000	$ 128
Payment of dispute resolution practices income tax percentage																				50.00%
Assessed income tax amount exclusive of interest and penalties																				$ 74,000,000														$ 107
Payment amount refund percentage																				50.00%
Tax assessment deposit					66,000,000																	66,000,000							$ 107
Other noncurrent liabilities and deferred credits (U)					206,000,000																$ 199,000,000	206,000,000		$ 199,000,000					$ 332		$ 293
Alcoa World Alumina Brasil [Member] \| Brazilian Federal Revenue Office [Member]
Loss Contingencies [Line Items]
Disallowed tax credits											$ 13,000,000				$ 4,000,000		$ 110,000,000															R$ 66,000,000	R$ 19,000,000				R$ 220,000,000
Percentage of penalty of the gross disallowed amount																	50.00%
Value added tax receivable					$ 1,000,000	R$ 6,000,000	$ 1,000,000	R$ 5,000,000	$ 6,000,000	R$ 31,000,000	$ 10,000,000	R$ 53,000,000	$ 9,000,000	R$ 44,000,000	$ 14,000,000	R$ 65,000,000		$ 41,000,000	R$ 82,000,000
Federal value added tax credits																											$ 136,000,000											R$ 273,000,000
Value added tax refund received																											$ 68,000,000	R$ 136,000,000
Alcoa Corporation [Member] \| AWAC [Member]
Loss Contingencies [Line Items]
Ownership interest percentage																														60.00%
Minimum [Member] \| Alcoa World Alumina Brasil [Member] \| Brazilian Federal Revenue Office [Member]
Loss Contingencies [Line Items]
Charge recorded in provision for income taxes to establish liability for estimated loss																						0
Maximum [Member] \| Alcoa World Alumina Brasil [Member] \| Brazilian Federal Revenue Office [Member]
Loss Contingencies [Line Items]
Charge recorded in provision for income taxes to establish liability for estimated loss																						$ 48,000,000	R$ 300,000,000
Aviles and La Coruna Smelters [Member] \| Maximum [Member] \| Parter Capital Group A G \| Spain [Member] \| Aviles and La Coruea Aluminum Facilities [Member]
Loss Contingencies [Line Items]
Financial Contributions																										$ 95,000,000
Financial contributions paid to buyer in relation to divestiture																										$ 78,000,000
Aviles and La Coruna Facilities [Member]
Loss Contingencies [Line Items]
Restructuring and other charges, net (D)																									$ 79,000,000