Other Financial Information - Additional Information (Details) $ in Millions	1 Months Ended
Jun. 30, 2022 USD ($)
Other Financial Information [Abstract]
Reversed the allowance with credit of restructuring and other charges, net	$ 83
Valuation allowance with credit to cost of goods sold	$ 46

Reversed the allowance with credit of restructuring and other charges, net.

No definition available.

Name:	aa_ReversedAllowanceWithCreditOfRestructuringAndOtherChargesNet
Namespace Prefix:	aa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration