Debt - Description of long-term debt (Details) - USD ($) $ in Millions	1 Months Ended
May 31, 2025	Jun. 30, 2025	Dec. 31, 2024
Long-term debt [Line Items]
Outstanding borrowings		$ 11,706	$ 11,030
Senior Revolving Credit Facility
Long-term debt [Line Items]
Maximum borrowing capacity		3,750
Maximum allowed letters of credit		200
Additional borrowing capacity, uncommitted loans		1,000
Outstanding borrowings		0
Outstanding letters of credit		0
Unused availability		3,750
Guaranteed Notes due 2035, $500 million, 6.150% ($1 million of discount, $5 million of debt issuance cost \| Issued by LYB International Finance III LLC:
Long-term debt [Line Items]
Outstanding borrowings		494	$ 0
Face amount	$ 500	$ 500
Stated interest rate (in percent)	6.15%	6.15%
Discount price	99.70%
Net proceeds from debt	$ 494
Redemption price (in percent)	100.00%

Additional borrowing capacity available under credit agreements through uncommitted accordion features.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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Amount of long-term debt and lease obligation, including portion classified as current.

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