Debt instrument capitalization ratio.

No definition available.

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- Definition

Debt instrument covenant leverage ratio.

+ References

No definition available.

+ Details

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- Definition

Debt maturity date of facility subsequently extended by number of year.

+ References

No definition available.

+ Details

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Namespace Prefix:	aa_
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Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility expiration month and year.

+ References

No definition available.

+ Details

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Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility repayment due date.

+ References

No definition available.

+ Details

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Namespace Prefix:	aa_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
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-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
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+ Details

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Balance Type:	debit
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- Details

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- Details

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- Details

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- Details

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Debt (Credit Facility) - Additional Information (Detail) kr in Billions				12 Months Ended
	Jun. 27, 2022 USD ($)	Jun. 26, 2022 USD ($)	Oct. 02, 2019 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Apr. 08, 2020 USD ($)	Oct. 02, 2019 NOK (kr)
One-year, Multicurrency Agreement [Member] \| Alcoa Norway ANS [Member]
Debt Instrument [Line Items]
Line of credit facility, current outstanding				$ 0
Debt instrument expiration date				Oct. 04, 2021
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 1,250,000,000	$ 1,500,000,000
Line of credit facility, maturity month and year	2027-06	2023-11
Principal amount of debt				$ 0	$ 0
Amounts borrowed under the credit facility				$ 0	$ 0
Revolving Credit Facility [Member] \| One-year, Multicurrency Agreement [Member] \| Alcoa Norway ANS [Member]
Debt Instrument [Line Items]
Principal amount of debt			$ 149,000,000				kr 1.3
Debt instrument, term			1 year
Debt maturity date of facility subsequently extended by number of year			1 year
Line of credit facility, current outstanding						$ 100,000,000
Line of credit facility, interest rate at period end						2.93%
Line of credit facility repayment due date				Jun. 29, 2020
Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Leverage ratio	3.25%	2.75%
Debt to capitalization ratio	0.60%