Investments - Additional Information (Detail) $ in Millions		1 Months Ended	12 Months Ended
	Feb. 15, 2022 USD ($)	Jun. 30, 2019	Dec. 31, 2023 USD ($)	Dec. 31, 2023 CAD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Schedule of Equity Method Investments [Line Items]
Dividends from equity investments			$ 51,000,000		$ 127,000,000	$ 50,000,000
Combined investment in joint venture			969,000,000		1,112,000,000
Asset impairments			$ 50,000,000		58,000,000	$ 75,000,000
Maaden Alcoa Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Non-controlling interest, ownership percentage			25.10%
Equity investments			$ 533,000,000		710,000,000
ELYSIS TM Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Basis in investment, due to share of losses			0
Unrecognized losses			$ (60,000,000)
Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in joint venture			25.10%	25.10%
Alcoa Corporation [Member] | Other Expenses (Income) [Member]
Schedule of Equity Method Investments [Line Items]
Charges recorded					$ 21,000,000
Adjustment recorded			$ 41,000,000
Alcoa Corporation [Member] | ELYSIS TM Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage			48.235%	48.235%
Contribution to joint venture			$ 118,000,000	$ 155
Overhead expenses			$ 3,000,000
Rio Tinto Plc [Member] | ELYSIS TM Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage			48.235%	48.235%
Quebec Provincial Government [Member] | ELYSIS TM Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Limited partner ownership interest percentage			3.53%	3.53%
Saudi Arabia [Member] | Ma'aden [Member] | Maaden Alcoa Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in joint venture			74.90%	74.90%
Brazil [Member] | Mineracao Rio Do Norte S A
Schedule of Equity Method Investments [Line Items]
Proceeds from Sale of Long-term Investments	$ 10,000,000
Asset impairments	58,000,000
Additional cash to be received upon satisfying post closing conditions	$ 30,000,000
Ma'aden Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Joint venture shareholders agreement period, years			30 years	30 years
Joint venture shareholders agreement, automatic extension additional period, years			20 years	20 years
Ma'aden Joint Venture [Member] | Saudi Arabia [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage transferred		25.10%
Alcoa Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Equity interest		0.00%