Debt instrument covenant interest expense coverage 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 instrument covenant leverage ratio, possible increase.

+ References

No definition available.

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- Definition

Debt instrument maturity year.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Debt instrument redemption period.

+ References

No definition available.

+ Details

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- Definition

Line of credit facility maximum additional borrowing capacity.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

Date the debt agreement requires the first payment to be made, in YYYY-MM-DD format.

+ References

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- Definition

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

+ References

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-Name Accounting Standards Codification
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- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

+ References

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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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

No definition available.

+ Details

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- Definition

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

+ References

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-SubTopic 10
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-Subparagraph (SX 210.5-02.22(a)(2))
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-Paragraph 2
-Subparagraph (bbb)(2)
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- Definition

Description of debt redemption features under terms of the debt agreement.

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- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

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- 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

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Balance Type:	credit
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- 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.

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-Paragraph 1
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Balance Type:	credit
Period Type:	instant

- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) of the credit facility.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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Balance Type:	credit
Period Type:	duration

- 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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Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow for the settlement of long-term borrowing, with the highest claim on the assets of the entity in case of bankruptcy or liquidation, as it matures.

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-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3291-108585

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- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

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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

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Debt - Additional Information (Detail) kr in Billions					1 Months Ended	3 Months Ended			9 Months Ended
Debt - Additional Information (Detail) kr in Billions	Apr. 07, 2021 USD ($)	Apr. 01, 2021 USD ($)	Mar. 04, 2021 USD ($)	Mar. 03, 2021	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Oct. 02, 2019 NOK (kr)
Debt Instrument [Line Items]
U.S. defined benefit pension plans, company's contribution		$ 500,000,000
Premium paid on early redemption of debt									$ 43,000,000
4.125% Senior Notes due 2029 [Member] \| Alcoa Nederland Holding BV [Member]
Debt Instrument [Line Items]
Senior notes, interest percentage					4.125%			4.125%
Debt instrument maturity date					2029
Principal amount of debt					$ 500,000,000			$ 500,000,000
Proceeds from issuance of debt					$ 493,000,000
U.S. defined benefit pension plans, company's contribution		500,000,000
Debt instrument, frequency of periodic payment									semi-annually
Debt instrument, date of first required payment					Sep. 30, 2021
6.75% Notes, due 2024 [Member]
Debt Instrument [Line Items]
Debt instrument maturity date	2024
Redemption of senior note	$ 750,000,000
Premium paid on early redemption of debt							$ 32,000,000
6.75% Notes, due 2024 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument redemption price percentage	103.375%
6.75% Notes, due 2024 [Member] \| Alcoa Nederland Holding BV [Member]
Debt Instrument [Line Items]
Senior notes, interest percentage					6.75%			6.75%
Debt instrument maturity date					2024
Principal amount of debt					$ 750,000,000			$ 750,000,000
5.500% Senior Notes due 2029 [Member] \| Alcoa Nederland Holding BV [Member]
Debt Instrument [Line Items]
Debt redemption description									ANHBV has the option to redeem the 2029 Notes on at least 10 days, but not more than 60 days, prior notice to the holders of the 2029 Notes under multiple scenarios, including, in whole or in part, at any time or from time to time after March 31, 2024, at a redemption price specified in the indenture (up to 102.063% of the principal amount plus any accrued and unpaid interest in each case). Also, the 2029 Notes are subject to repurchase upon the occurrence of a change in control repurchase event (as defined in the indenture) at a repurchase price in cash equal to 101% of the aggregate principal amount of the 2029 Notes repurchased, plus any accrued and unpaid interest on the 2029 Notes repurchased.
5.500% Senior Notes due 2029 [Member] \| Alcoa Nederland Holding BV [Member] \| Maximum [Member] \| After June 15, 2023 [Member]
Debt Instrument [Line Items]
Debt instrument redemption period									60 days
Debt instrument redemption price percentage									102.063%
5.500% Senior Notes due 2029 [Member] \| Alcoa Nederland Holding BV [Member] \| Maximum [Member] \| Change in Control [Member]
Debt Instrument [Line Items]
Debt instrument redemption price percentage									101.00%
5.500% Senior Notes due 2029 [Member] \| Alcoa Nederland Holding BV [Member] \| Minimum [Member] \| After June 15, 2023 [Member]
Debt Instrument [Line Items]
Debt instrument redemption period									10 days
7.00% Notes, due 2026 [Member]
Debt Instrument [Line Items]
Senior notes, interest percentage						7.00%			7.00%
Debt instrument maturity date									2026
Redemption of senior note									$ 500,000,000
Premium paid on early redemption of debt						$ 22,000,000
7.00% Notes, due 2026 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument redemption price percentage									103.50%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, term									1 year
Line of credit facility, current outstanding			$ 1,500,000,000			0			$ 0
Line of credit facility, maximum additional borrowings			$ 750,000,000			4,944,000,000			4,944,000,000
Amounts borrowed under the credit facility						0			0
Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Leverage ratio			275.00%	250.00%
Leverage ratio, maximum possible increase			300.00%
Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest expense coverage ratio required to be maintained			4.00	5.00
Revolving Credit Facility [Member] \| One-year, Multicurrency Agreement [Member] \| Alcoa Norway ANS [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum outstanding borrowings						149,000,000			$ 149,000,000	kr 1.3
Debt instrument expiration date									Oct. 04, 2021
Line of credit facility, current outstanding						$ 0			$ 0
Revolving Credit Facility [Member] \| 5.500% Senior Notes due 2027 [Member]
Debt Instrument [Line Items]
Line of credit facility, decrease in aggregate amount of commitments								245,000,000
Line of credit facility, aggregate amount of commitments		$ 1,500,000,000						$ 1,255,000,000
Senior notes, interest percentage					5.50%			5.50%
Debt instrument maturity date								2027