Restructuring and Other Charges, Net (2021 Actions) - Additional Information (Detail) kt in Thousands, $ in Millions	1 Months Ended		3 Months Ended		12 Months Ended
	Dec. 31, 2021 USD ($) Employee kt	Sep. 30, 2019 USD ($) Employee	Dec. 31, 2021 USD ($) Employee	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) Employee Retiree	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					$ 1,128	$ 104	$ 1,031
Number of employees under defined benefit plan | Employee	14,000		14,000		14,000
Settlement and curtailment of certain other postretirement benefits					$ (977)	(58)	(119)
Asset impairments					75	2	225
Severance costs		$ 37			1	16	51
Number of employees associated with employee termination and severance costs | Employee		260
Payments for restructuring					29	120	118
Asset retirement obligation	$ 738		$ 738		738	753	$ 717
Curtailed Aluminum Smelter Facility [Member] | Lake Charles (Louisiana) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				$ 27
Asset impairments				22
Asset retirement obligation				$ 5
Wenatchee (Washington) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			80
Charges for write-off remaining net book value of assets.			30
Asset impairments			23
Severance costs			$ 1
Number of employees associated with employee termination and severance costs | Employee			10
Wenatchee (Washington) [Member] | Curtailed Aluminum Smelter Facility [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					80
Lake Charles (Louisiana) [Member] | Curtailed Aluminum Smelter Facility [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					27
San Ciprian Facility [Member]
Restructuring Cost and Reserve [Line Items]
Curtailment of smelting capacity | kt	228
San Ciprian Facility [Member] | Curtailed Aluminum Smelter Facility [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			$ 62		62
Restricted cash	$ 103		103		103
Capital improvement costs	68
Restart costs	35
Alumar Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					(6)
Avilés and La Coruña Aluminum Facilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					(17)
Severance and Exit Costs [Member] | Warrick Rolling Mill [Member]
Restructuring Cost and Reserve [Line Items]
Settlement and curtailment of certain other postretirement benefits					9
Contract Termination [Member] | Wenatchee (Washington) and Intalco (Washington) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					13
Additional Environmental and Asset Retirement [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					11
Other Item Charges [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					3
Permanent Close [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					(22)
Closure Cost [Member] | Wenatchee (Washington) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			90
Decommissioning and Demolition | Wenatchee (Washington) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			21
Cost of Goods Sold [Member] | Wenatchee (Washington) [Member]
Restructuring Cost and Reserve [Line Items]
Other costs			10
Group Annuity Contract [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					858
Plan obligations	$ 55		$ 55		55
Plan assets					$ 55
Number of retirees | Retiree					800
Group Annuity Contract [Member] | Restructuring And Other Charges [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					$ 63
Pension Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					$ 1,500
Number of employees under defined benefit plan | Employee	37,000		37,000		37,000
Plan obligations	$ 4,594		$ 4,594		$ 4,594	$ 6,904
Settlement of certain pension benefits					47
2021 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net					$ 1,128