Segment Information - Schedule of Segment Adjusted EBITDA to Consolidated Net Income Attributable to Alcoa Corporation (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 236	$ 784	$ 2,193	$ 1,978
Transformation	(19)	(10)	(44)	(34)
Intersegment eliminations	17	(8)	139	20
Corporate expenses	(27)	(30)	(91)	(84)
Provision for depreciation, depletion, and amortization	(149)	(156)	(470)	(499)
Restructuring and other charges, net (D)	(652)	(33)	(702)	(73)
Interest expense	(25)	(58)	(80)	(167)
Other (income) expense, net (Q)	(35)	18	185	147
(Loss) income before income taxes	(729)	497	942	1,270
Provision for income taxes	(40)	(127)	(484)	(331)
Net loss (income) attributable to noncontrolling interest	23	(33)	(186)	(118)
NET (LOSS) INCOME ATTRIBUTABLE TO ALCOA CORPORATION	(746)	337	272	821
Other [Member]
Segment Reporting Information [Line Items]
Restructuring and other charges, net (D)	(652)	(33)	(702)	(73)
Other	$ (75)	$ (10)	$ (188)	$ (18)