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Percentage of penalty on amount of additional taxes due.

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Proposed administrative penalties.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Includes expenses related to certain asset retirement obligations.

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Tax assessment deposit.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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Amount of increase (decrease) to previously recorded tax expense. Includes, but is not limited to, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, and IRS tax settlement.

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Contingencies - Additional Information - 1 (Detail) $ in Millions			1 Months Ended											3 Months Ended									9 Months Ended
	Sep. 17, 2020 USD ($)	Sep. 17, 2020 AUD ($)	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$)	Sep. 30, 2022 USD ($)	Sep. 30, 2022 AUD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2022 BRL (R$)	Sep. 30, 2021 USD ($)	Sep. 30, 2021 AUD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 AUD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2022 AUD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 AUD ($)	Jul. 31, 2022 BRL (R$)	Feb. 28, 2022 BRL (R$)	Dec. 31, 2021 USD ($)	Sep. 30, 2020 AUD ($)	Jul. 07, 2020 USD ($)	Jul. 07, 2020 AUD ($)	Mar. 31, 2013 BRL (R$)
Loss Contingencies [Line Items]
Other noncurrent liabilities and deferred credits														$ 442,000,000									$ 442,000,000						$ 599,000,000
Restructuring and other charges, net																							$ 702,000,000		$ 73,000,000
Aviles And La Coruna Facilities [Member]
Loss Contingencies [Line Items]
Restructuring and other charges, net																$ 2,000,000	$ 77,000,000
AWAC [Member] \| Alumina Limited [Member]
Loss Contingencies [Line Items]
Non-controlling interest, ownership percentage														40.00%									40.00%			40.00%
Australian Taxation Office [Member] \| Foreign Jurisdiction [Member] \| AofA [Member]
Loss Contingencies [Line Items]
Additional income tax payable, exclusive of interest and penalties																															$ 139,000,000	$ 214
Notices include claims for compounded interest on the tax amount																															$ 460,000,000	$ 707
Proposed administrative penalties	$ 83,000,000	$ 128
Payment of dispute resolution practices income tax percentage																					50.00%	50.00%
Assessed income tax amount exclusive of interest and penalties																					$ 74,000,000									$ 107
Payment amount refund percentage																					50.00%	50.00%
Reduction in current year cash tax payment														$ 10,000,000	$ 16				$ 14,000,000	$ 19	$ 169,000,000	$ 219	$ 10,000,000	$ 16
Other noncurrent liabilities and deferred credits														165,000,000									165,000,000			$ 254
Tax assessment deposit														$ 69,000,000									$ 69,000,000			$ 107
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$ 70,000,000	R$ 19,000,000					R$ 220,000,000
Percentage of penalty of the gross disallowed amount											50.00%
Value added tax receivable			$ 6,000,000	R$ 31,000,000	$ 16,000,000	R$ 84,000,000	$ 9,000,000	R$ 44,000,000	$ 14,000,000	R$ 65,000,000		$ 41,000,000	R$ 82,000,000
Alcoa Corporation [Member] \| AWAC [Member]
Loss Contingencies [Line Items]
Ownership interest percentage														60.00%									60.00%			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																	$ 44,000,000	R$ 239,000,000