Contingencies, Commitments and Other Liabilities (Details) € in Millions, $ in Millions			1 Months Ended			3 Months Ended		12 Months Ended
	Jun. 15, 2023 USD ($) installment	Jan. 01, 2023	Jul. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jul. 31, 2023 USD ($)	Mar. 31, 2024 USD ($) location	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2023 EUR (€)	Dec. 31, 2023 EUR (€)	Mar. 31, 2023 EUR (€)	Jun. 26, 2020 entity transaction
Loss Contingencies [Line Items]
Number of cleanup locations | location						30
Remediation reserve balance				$ 17		$ 17		$ 17
Remediation reserve balance, classified as a current liability				7		7		7
Payments related to remediation expenses applied against the reserve						1	$ 1
Income tax reserve						0	20
Guarantees of third party related to project financing						25
Combined fair value of guarantees				6		6		$ 6
Coverage limit				$ 80
Total amount committed under outstanding surety bonds						43
Surety bonds, amount outstanding						$ 21
Termination notice period (in days)		30 days
Payment timing (in days)		120 days
Supplier Finance Program, Obligation, Current, Statement of Financial Position [Extensible Enumeration]				Accounts payable, trade (P)		Accounts payable, trade (P)		Accounts payable, trade (P)		Accounts payable, trade (P)
Supplier invoices subject to future payment				$ 258		$ 269		$ 258
Letter of Credit
Loss Contingencies [Line Items]
Maximum borrowing capacity						96
Other Noncurrent Liabilities and Deferred Credits | Separation Agreement
Loss Contingencies [Line Items]
Guarantees of third party related to project financing				1,131		1,131		1,131
Lehman Brothers International (Europe) (“LBIE”) Claims
Loss Contingencies [Line Items]
Number of entities | entity												2
Number of interest rate swap transactions | transaction												2
Judgement from legal proceedings	$ 40
Number of installment payments | installment	2
Payments for legal settlements					$ 15
Lehman Brothers International (Europe) (“LBIE”) Claims | Forecast | Subsequent Event
Loss Contingencies [Line Items]
Payments for legal settlements			$ 25
Foreign Tax Authority | Ministry of the Economy, Finance and Industry, France | Tax Years 2010 Through 2012
Loss Contingencies [Line Items]
Assessment amount				$ 2			$ 18	2		€ 2	€ 16
Income tax reserve								$ 21	€ 19
Alcoa Corporation Workers Compensation Claims
Loss Contingencies [Line Items]
Letters of credit, total amount outstanding						52
Arconic Corporation Environmental Obligations
Loss Contingencies [Line Items]
Letters of credit, total amount outstanding						$ 17
Maximum | Recurring Costs of Managing Hazardous Substances and Environmental Programs
Loss Contingencies [Line Items]
Percentage of cost of goods sold (as a percent)						1.00%