Other Financial Information - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 30, 2016 Refinery	Dec. 31, 2021 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) Subsidiary	Dec. 31, 2019 USD ($)	Dec. 29, 2021 USD ($)
Other Non operating Income Expense [Line Items]
Net gain from asset sales				$ 354	$ 173	$ 3
Number of alumina refineries to be powered under supplied agreement | Refinery	3
VAT credits payable		$ 47		47
Sales				12,152	9,286	10,433
Deferred carbon dioxide emission credits		(54)		(54)	(56)
Restricted cash		106		106			$ 103
San Ciprián Smelter [Member]
Other Non operating Income Expense [Line Items]
Deferred carbon dioxide emission credits		(40)		(40)
Refinery [Member]
Other Non operating Income Expense [Line Items]
Deferred carbon dioxide emission credits		(6)		(6)
Dampier to Bunbury Natural Gas Pipeline [Member] | AofA [Member]
Other Non operating Income Expense [Line Items]
Investment percentage	30.00%
Prepayments made under the agreement for future gas transmission services		304		304	315
Brazil [Member]
Other Non operating Income Expense [Line Items]
Sales				610	$ 346	$ 428
Brazil [Member] | Alcoa World Alumina Brazil and Alcoa Aluminio [Member]
Other Non operating Income Expense [Line Items]
Number of subsidiaries | Subsidiary					2
Sales		34
Restructuring and other charges, net			$ 107
Brazil [Member] | Alcoa World Alumina Brazil and Alcoa Aluminio [Member] | Other Noncurrent Assets [Member]
Other Non operating Income Expense [Line Items]
Additional VAT credits recorded		95
Brazil [Member] | Alcoa World Alumina Brazil and Alcoa Aluminio [Member] | Other Income Expenses [Member]
Other Non operating Income Expense [Line Items]
Interest income		14
Brazil [Member] | Alcoa World Alumina Brazil and Alcoa Aluminio [Member] | Other Noncurrent Liabilities [Member]
Other Non operating Income Expense [Line Items]
VAT credits payable		47		47
Gum Springs [Member]
Other Non operating Income Expense [Line Items]
Net gain from asset sales					$ 181
Eastalco Site Sale And Warrick Rolling Mill [Member]
Other Non operating Income Expense [Line Items]
Net gain from asset sales				354
Avilés and La Coruña Facilities [Member]
Other Non operating Income Expense [Line Items]
Deferred carbon dioxide emission credits		$ (8)		$ (8)