Investments - Summary of Profit and Loss Information for Alcoa Corporation's Equity Investments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Net (loss) income	$ (773)	$ 38	$ 570
Ma'aden Joint Venture [Member] | Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Alcoa Corporation's equity in net (loss) income of affiliated companies	(158)	4	116
Ma'aden Joint Venture [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Sales	2,726	3,317	3,127
Cost of goods sold	2,550	2,696	2,083
Net (loss) income	(457)	42	495
Equity in net (loss) income of affiliated companies, before reconciling adjustments	(115)	11	124
Other	(43)	(7)	(8)
Mining [Member] | Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Alcoa Corporation's equity in net (loss) income of affiliated companies	23	37	23
Mining [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Sales	670	763	794
Cost of goods sold	446	488	571
Net (loss) income	50	110	30
Equity in net (loss) income of affiliated companies, before reconciling adjustments	23	39	18
Other	0	(2)	5
Energy [Member] | Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Alcoa Corporation's equity in net (loss) income of affiliated companies	40	38	44
Energy [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Sales	236	252	264
Cost of goods sold	118	120	135
Net (loss) income	100	109	114
Equity in net (loss) income of affiliated companies, before reconciling adjustments	39	41	45
Other	1	(3)	(1)
Other [Member] | Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Alcoa Corporation's equity in net (loss) income of affiliated companies	(55)	(21)	5
Other [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Sales	464	488	404
Cost of goods sold	425	445	365
Net (loss) income	(97)	(75)	(42)
Equity in net (loss) income of affiliated companies, before reconciling adjustments	(46)	(36)	(20)
Other	$ (9)	$ 15	$ 25