Curtailment of smelting capacity.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from settlement and curtailment.

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Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

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Restructuring and Other Charges, Net - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) kt	Dec. 31, 2020 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)	$ 652	$ 33	$ 702	$ 73
Restructuring reserve	121		121		$ 93	$ 63
Cash payments for restructuring			28		29
Noncurrent portion of the reserve	11		11		$ 43
MRN [Member]
Restructuring Cost And Reserve [Line Items]
Asset impairment charges			58
Pension Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Settlement of certain other postretirement benefits	626	8	626	47
San Ciprian Facility [Member]
Restructuring Cost And Reserve [Line Items]
Curtailment of smelting capacity \| kt					228,000
Cash payments for restructuring	9		17
Magnesium Smelter Facility in Addy [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)	29		29
Curtailed Anode Facility [Member] \| Lake Charles, Louisiana [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)		27		27
Asset impairment charges		22
Asset retirement obligation		5		5
Curtailed Aluminum Smelter Facility [Member] \| San Ciprian Facility [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve					$ 62
Valuation Allowance on Brazil Value-Added Taxes [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)			(83)
Additional Contract Costs [Member] \| Wenatchee (Washington) and Intalco (Washington) [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)		2	(6)	11
Remediation at Previously Closed Sites [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)	$ (3)		(1)
Legal Disputes Related to 2019 Divestiture [Member] \| Avil?s and La Coru?a Facilities [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)			$ 79
Permanent Close [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)				(22)
Permanent Close [Member] \| Brazil [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)		(6)		(6)
Severance and Exit Costs [Member]
Restructuring Cost And Reserve [Line Items]
Settlement and curtailment of certain other postretirement benefits				9
Other Item Charges [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net (D)		$ 2		$ 7