Contingencies and Commitments - Additional Information - 1 (Detail) € in Millions, $ in Millions			1 Months Ended			3 Months Ended						6 Months Ended		12 Months Ended
	Sep. 17, 2020 USD ($)	Sep. 17, 2020 AUD ($)	Mar. 31, 2013 USD ($)	May 31, 2012 USD ($)	May 31, 2012 BRL (R$)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 EUR (€)	Sep. 30, 2020 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 EUR (€)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 AUD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 AUD ($)	Dec. 31, 2021 BRL (R$)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 AUD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 EUR (€)	Dec. 31, 2021 AUD ($)	Sep. 30, 2020 AUD ($)	Jul. 07, 2020 USD ($)	Jul. 07, 2020 AUD ($)	Mar. 31, 2013 BRL (R$)
Loss Contingencies [Line Items]
Other noncurrent liabilities and deferred credits (U)						$ 599,000,000	$ 515,000,000					$ 515,000,000		$ 599,000,000			$ 515,000,000
AWAC [Member] | Alumina Limited [Member]
Loss Contingencies [Line Items]
Non-controlling interest, ownership percentage						40.00%								40.00%								40.00%
Alcoa Corporation [Member] | AWAC [Member]
Loss Contingencies [Line Items]
Ownership interest percentage						60.00%								60.00%								60.00%
PARTER Capital Group AG [Member] | Spain [Member] | Aviles and La Coruna Smelters [Member] | Avilés and La Coruña Aluminum Facilities [Member]
Loss Contingencies [Line Items]
Financial contributions														$ 13,000,000			38,000,000
Minimum [Member]
Loss Contingencies [Line Items]
Estimated range of reasonably possible loss						$ 0								0
Maximum [Member]
Loss Contingencies [Line Items]
Estimated range of reasonably possible loss						70,000,000								70,000,000
Maximum [Member] | PARTER Capital Group AG [Member] | Spain [Member] | Aviles and La Coruna Smelters [Member] | Avilés and La Coruña Aluminum Facilities [Member]
Loss Contingencies [Line Items]
Financial contributions														95,000,000					$ 95,000,000
Financial contributions paid to buyer in relation to divestiture														78,000,000
Reversal of Remaining Reserve						17,000,000
Tax Authority, Spain [Member]
Loss Contingencies [Line Items]
Charge recorded in provision for income taxes to establish liability for estimated loss										$ 30,000,000	€ 26									$ 30,000,000	€ 26
Reversal of reserve recorded in provision for income taxes to establish liability for estimated loss							$ 32,000,000	€ 26
Brazilian Federal Revenue Office [Member] | Alcoa World Alumina Brasil [Member]
Loss Contingencies [Line Items]
Disallowed tax credits			$ 110,000,000																							R$ 220,000,000
Percentage of penalty of the gross disallowed amount			50.00%
Value added tax receivable				$ 41,000,000	R$ 82,000,000
Brazilian Federal Revenue Office [Member] | Minimum [Member] | Alcoa World Alumina Brasil [Member]
Loss Contingencies [Line Items]
Charge recorded in provision for income taxes to establish liability for estimated loss														0
Brazilian Federal Revenue Office [Member] | Maximum [Member] | Alcoa World Alumina Brasil [Member]
Loss Contingencies [Line Items]
Charge recorded in provision for income taxes to establish liability for estimated loss														39,000,000		R$ 220,000,000
Australian Taxation Office [Member] | Foreign [Member]
Loss Contingencies [Line Items]
Assessed income tax amount exclusive of interest and penalties									$ 74,000,000														$ 107
Reduction in current year cash tax payment												$ 169,000,000	$ 219	14,000,000	$ 19
Australian Taxation Office [Member] | Foreign [Member] | AofA [Member]
Loss Contingencies [Line Items]
Additional income tax payable, exclusive of interest and penalties																								$ 156,000,000	$ 214
Notices include claims for compounded interest on the tax amount																								$ 516,000,000	$ 707
Proposed administrative penalties	$ 94,000,000	$ 128
Payment of dispute resolution practices income tax percentage									50.00%
Assessed income tax amount exclusive of interest and penalties									$ 74,000,000														$ 107
Payment amount refund percentage									50.00%
Reduction in current year cash tax payment														14,000,000	$ 19		$ 169,000,000	$ 219
Tax assessment deposit						78,000,000								78,000,000								$ 107
Other noncurrent liabilities and deferred credits (U)						$ 174,000,000								$ 174,000,000								$ 238