Contingencies and Commitments - Additional Information - 2 (Detail) $ in Millions		1 Months Ended	12 Months Ended
	Apr. 08, 2015 USD ($) Refinery	Apr. 30, 2016 Refinery	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2023 AUD ($)	Aug. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Number of alumina refineries to be powered under supplied agreement | Refinery		3
Total asset			$ 283,000,000	$ 311,000,000
Guarantees of third party related to project financing			$ 0	0
Line of credit renew or expire starting year			2024
Line of credit renew or expire ending year			2025
Letters of credit, total amount committed			$ 294,000,000
Letter of credit agreement, expiration date			Jun. 27, 2024
Total amount committed under outstanding surety bonds			$ 190,000,000
Minimum [Member]
Loss Contingencies [Line Items]
Surety bonds, expiration date			2024
Maximum [Member]
Loss Contingencies [Line Items]
Surety bonds, expiration date			2028
Alcoa Corporation [Member]
Loss Contingencies [Line Items]
Outstanding bank guarantees and letters of credit			$ 13,000,000
Total amount committed under outstanding surety bonds			8,000,000
Parent Co [Member]
Loss Contingencies [Line Items]
Outstanding bank guarantees and letters of credit			8,000,000
Total amount committed under outstanding surety bonds			5,000,000
Standby Letter of Credit Agreement [Member]
Loss Contingencies [Line Items]
Line of credit facility, outstanding borrowings			86,000,000
Principal amount of debt							$ 200,000,000
Letter of Credit [Member]
Loss Contingencies [Line Items]
Line of credit facility, outstanding borrowings			86,000,000
AofA [Member]
Loss Contingencies [Line Items]
Bank guarantee			68,000,000			$ 100
AofA [Member] | Service Agreements [Member] | Alcoa Corporation [Member]
Loss Contingencies [Line Items]
Number of alumina refineries to be powered under supplied agreement | Refinery	3
Gas supply agreement prepayment amount	$ 500,000,000
AofA [Member] | Service Agreements [Member] | Prepaid Expenses and Other Current Assets [Member] | Alcoa Corporation [Member]
Loss Contingencies [Line Items]
Total asset			37,000,000	37,000,000
AofA [Member] | Service Agreements [Member] | Other Noncurrent Assets [Member] | Alcoa Corporation [Member]
Loss Contingencies [Line Items]
Total asset			$ 283,000,000	311,000,000
Energy Obligation [Member]
Loss Contingencies [Line Items]
Expiration date of unconditional purchase obligations for energy starting year			2040
Expiration date of unconditional purchase obligations for energy ending year			2041
Purchase obligations due in 2024			$ 56,000,000
Purchase obligations due in 2025			59,000,000
Purchase obligations due in 2026			61,000,000
Purchase obligations due in 2027			63,000,000
Purchase obligations due in 2028			65,000,000
Purchase obligations due thereafter			770,000,000
Purchase obligations expenditures			53,000,000	$ 58,000,000	$ 86,000,000
Energy Raw Materials And Other Goods And Services [Member]
Loss Contingencies [Line Items]
Purchase obligations due in 2024			3,896,000,000
Purchase obligations due in 2025			1,998,000,000
Purchase obligations due in 2026			1,566,000,000
Purchase obligations due in 2027			1,448,000,000
Purchase obligations due in 2028			1,407,000,000
Purchase obligations due thereafter			$ 8,757,000,000