Investments - Summary of Profit and Loss Information for Alcoa Corporation's Equity Investments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Net income (loss)	$ 38	$ 570	$ (14)
Ma'aden Joint Venture [Member] | Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Alcoa Corporation’s equity in net income (loss) of affiliated companies	4	116	(34)
Ma'aden Joint Venture [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Sales	3,317	3,127	2,279
Cost of goods sold	2,696	2,083	1,829
Net income (loss)	42	495	(108)
Equity in net income (loss) of affiliated companies, before reconciling adjustments	11	124	(27)
Other	(7)	(8)	(7)
Mining [Member] | Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Alcoa Corporation’s equity in net income (loss) of affiliated companies	37	23	22
Mining [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Sales	763	794	841
Cost of goods sold	488	571	543
Net income (loss)	110	30	46
Equity in net income (loss) of affiliated companies, before reconciling adjustments	39	18	23
Other	(2)	5	(1)
Energy [Member] | Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Alcoa Corporation’s equity in net income (loss) of affiliated companies	38	44	33
Energy [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Sales	252	264	238
Cost of goods sold	120	135	107
Net income (loss)	109	114	74
Equity in net income (loss) of affiliated companies, before reconciling adjustments	41	45	31
Other	(3)	(1)	2
Other [Member] | Alcoa Corporation [Member]
Schedule of Equity Method Investments [Line Items]
Alcoa Corporation’s equity in net income (loss) of affiliated companies	(21)	5	3
Other [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Sales	488	404	316
Cost of goods sold	445	365	283
Net income (loss)	(75)	(42)	(24)
Equity in net income (loss) of affiliated companies, before reconciling adjustments	(36)	(20)	(11)
Other	$ 15	$ 25	$ 14