Statement of Consolidated Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss) attributable to Alcoa Corporation	$ 429	$ (170)	$ (1,125)
Net income (loss), Noncontrolling interest	141	156	272
Net income (loss)	570	(14)	(853)
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits, Alcoa Corporation	1,654	(254)	1
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits, Noncontrolling interest	54	(11)	(10)
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	1,708	(265)	(9)
Foreign currency translation adjustments, Alcoa Corporation	(229)	(225)	(89)
Foreign currency translation adjustments, Noncontrolling interest	(93)	(10)	(24)
Foreign currency translation adjustments	(322)	(235)	(113)
Net change in unrecognized gains/losses on cash flow hedges, Alcoa Corporation	(388)	(176)	(321)
Net change in unrecognized gains/losses on cash flow hedges, Noncontrolling interest		(21)	(11)
Net change in unrecognized gains/losses on cash flow hedges	(388)	(197)	(332)
Total Other comprehensive income (loss), net of tax, Alcoa Corporation	1,037	(655)	(409)
Total Other comprehensive income (loss), net of tax, Noncontrolling interest	(39)	(42)	(45)
Total Other comprehensive income (loss), net of tax	998	(697)	(454)
Comprehensive income (loss), Alcoa Corporation	1,466	(825)	(1,534)
Comprehensive income (loss), Noncontrolling interest	102	114	227
Comprehensive income (loss)	$ 1,568	$ (711)	$ (1,307)