Derivatives and Other Financial Instruments - Additional Information (Detail) kt in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) Member Smelter kt	Dec. 31, 2022 USD ($) kt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Minimum members required for strategic risk management committee | Member	3
Realized loss reclassed from Other comprehensive (loss) income to earnings	$ (130)	$ (316)
Unrealized gain (loss) in accumulated other comprehensive loss	$ (3,645)	(3,539)
Other derivative contracts estimated term of quoted market prices, in years	10 years
Other derivative beyond market estimated quoted price of aluminum by extrapolating	10 years
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gain (loss) in accumulated other comprehensive loss	$ 11	20
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of smelters | Smelter	7
Level 1 Derivative Instruments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized loss reclassed from Other comprehensive (loss) income to earnings	$ 86	35
Commodity Contract | Level 1 [Member] | Brazil [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instrument, start date	Apr. 30, 2022
Commodity Contract | Level 1 [Member] | Brazil [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, expiration month and year	2023-12
Commodity Contract | Level 1 [Member] | Spain [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, expiration month and year	2022-10
Foreign Exchange Forward | Brazil [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, expiration month and year	2025-08
Foreign Exchange Forward | Norway [Member] | Euro Power Purchases [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, expiration month and year	2026-12
Foreign Exchange Forward | Norway [Member] | Krone Capital Expenditures [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, expiration month and year	2025-06
Foreign Exchange Forward | Canada [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, expiration month and year	2025-03
Sales [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized loss reclassed from Other comprehensive (loss) income to earnings	$ (31)	(10)
Cost of Goods Sold [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized loss reclassed from Other comprehensive (loss) income to earnings	(5)	(5)
Derivatives Designated as Hedging Instruments [Member] | Level 1 Derivative Instruments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized loss reclassed from Other comprehensive (loss) income to earnings	$ 86	$ 35
Derivatives Designated as Hedging Instruments [Member] | Power Contract [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aluminum forecast sales | kt	1,456	1,683
Derivatives Designated as Hedging Instruments [Member] | Power Contract [Member] | Cash Flow Hedging [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amount of gain (loss) expected to be recognized into earnings over the next 12 months	$ 210
Derivatives Designated as Hedging Instruments [Member] | Sales [Member] | Level 1 Derivative Instruments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized loss reclassed from Other comprehensive (loss) income to earnings	91	$ 40
Derivatives Designated as Hedging Instruments [Member] | Cost of Goods Sold [Member] | Level 1 Derivative Instruments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized loss reclassed from Other comprehensive (loss) income to earnings	$ (5)	$ (5)
Derivatives Not Designated as Hedging Instruments [Member] | Financial Contracts [Member] | Level 3 [Member] | LME Price and Power Price [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contract Termination	Jun. 30, 2026