Derivatives and Other Financial Instruments - Additional Information (Detail) kt in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) kt	Mar. 31, 2021 USD ($) Contract	Dec. 31, 2021 kt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized loss reclassed from Other comprehensive loss to earnings	$ (114)	$ (52)
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 to earnings	$ (6)
Commodity Contract | Level 1 [Member] | San Ciprian (Spain) Strike [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, expiration month and year	2022-04
Foreign Exchange Forward | U.S. dollar Aluminum Sales, Australia [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative, expiration date	Jun. 30, 2021
Foreign Exchange Forward | Euro Power Purchases, Norway [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 | Brazil [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, expiration month and year	2024-12
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 to earnings	$ (6)
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	1,849		1,905
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 (loss) gain expected to be recognized into earnings over the next 12 months	$ (386)
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 to earnings	(5)
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 to earnings	$ (1)
Derivatives Not Designated as Hedging Instruments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of financial contracts | Contract		4