Financial Instruments - Derivative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted		$ 136
Cash and cash equivalents	$ 4,758	5,208
Restricted cash and cash equivalents	1,208	1,034
Restricted Cash and Cash Equivalents, Noncurrent	97	98
Total cash and cash equivalents and restricted cash and cash equivalents presented in the consolidated statements of cash flows	$ 6,063	6,340	$ 7,104	$ 8,390
Export Proceeds, Percent	30.00%
Bank Time Deposits
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 300	100
Designated for Smelter Development Projects
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents and restricted cash and cash equivalents presented in the consolidated statements of cash flows	200
Designated For Export Proceeds
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents	1,100	900
Assurance Bonds
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents	$ 145	$ 147