Statement of Consolidated Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS) ATTRIBUTABLE TO ALCOA CORPORATION	$ 90	$ (168)	$ (142)	$ (501)
Net income (loss), Noncontrolling interest	8	(25)	(36)	(45)
Net income (loss)	98	(193)	(178)	(546)
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits, Alcoa Corporation	1	5	23	19
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits, Noncontrolling interest	(2)	(1)	4	(3)
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits	(1)	4	27	16
Foreign currency translation adjustments, Alcoa Corporation	144	(67)	(38)	(40)
Foreign currency translation adjustments, Noncontrolling interest	(35)	(47)	(105)	(21)
Foreign currency translation adjustments	109	(114)	(143)	(61)
Net change in unrecognized gains/losses on cash flow hedges, Alcoa Corporation	(51)	(91)	17	13
Net change in unrecognized gains/losses on cash flow hedges, Noncontrolling interest	1	0	0	0
Net change in unrecognized gains/losses on cash flow hedges	(50)	(91)	17	13
Total Other comprehensive income (loss), net of tax, Alcoa Corporation	94	(153)	2	(8)
Total Other comprehensive income (loss), net of tax, Noncontrolling interest	(36)	(48)	(101)	(24)
Total Other comprehensive income (loss), net of tax	58	(201)	(99)	(32)
Comprehensive income (loss), Alcoa Corporation	184	(321)	(140)	(509)
Comprehensive income (loss), Noncontrolling interest	(28)	(73)	(137)	(69)
Comprehensive income (loss)	$ 156	$ (394)	$ (277)	$ (578)