Related-Party and Party-In-Interest Transactions - Additional Information (Details) - EBP 004 & 003 - USD ($)	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Alcoa Corporation Stock Fund
EBP, Related Party and Party-in-Interest Transactions [Line Items]
Market value of purchases amount	$ 2,990,770
Market value of sales amount	5,138,270
Alcoa Corporation Common Stock
EBP, Related Party and Party-in-Interest Transactions [Line Items]
Dividends earned on common stock	$ 132,787
EBP, number of plans owned	259,732	291,433

Amount of increase in net asset available for benefit from dividend income on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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- Definition

Cost of investment, excluding plan interest in master trust, acquired by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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Number of shares or units of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
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-Name Employee Retirement Income Security Act of 1974
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- Definition

Amount of selling price for investment, excluding plan interest in master trust, sold by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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