Restructuring and Other Charges, Net (2020 Actions) - Additional Information (Detail) $ in Millions		12 Months Ended
	Apr. 22, 2020 kt	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) Employee	Dec. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net		$ 1,128	$ 104	$ 1,031
Settlements and curtailments of pension and other postretirement benefits		977	58	119
Net curtailment gain		17	(7)
Payments for restructuring		29	120	118
Intalco [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			$ 28
Curtailment of smelting capacity | kt	230
Curtailed smelting capacity | kt	49
Number of affected employees associated with employee termination and severance costs | Employee			685
Contract termination costs			$ 16
Net curtailment gain			1
Payments for restructuring			11
Payment of contract termination cost			5
2020 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			104
Settlements and curtailments of pension and other postretirement benefits			59
Severance and Exit Costs [Member] | 2020 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (reversal)			28
Contract Termination [Member] | 2020 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			20
Severance and Employee Termination Costs [Member]
Restructuring Cost and Reserve [Line Items]
Payments for restructuring		$ 4	41	$ 19
Severance and Employee Termination Costs [Member] | Intalco [Member] | Alcoa Corporation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			$ 13