Derivative financial instruments - Fair value of hedge ineffectiveness (Details) - Cash flow hedges - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Highly probable forecast capital expenditure \| Foreign exchange risk
Disclosure of detailed information about financial instruments [line items]
Change in fair value of hedging instrument used to calculate ineffectiveness	$ 1	$ 0
Change in fair value of hedged item used to calculate ineffectiveness	(1)	0
Hedge ineffectiveness recognized in profit or (loss)	0	0
Highly probable forecast sales \| Commodity price risk
Disclosure of detailed information about financial instruments [line items]
Change in fair value of hedging instrument used to calculate ineffectiveness	1,065	(825)
Change in fair value of hedged item used to calculate ineffectiveness	(1,065)	825
Hedge ineffectiveness recognized in profit or (loss)	$ 0	$ 0

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The gain (loss) on the change in fair value of the hedged item used as a basis for recognising hedge ineffectiveness. Hedge ineffectiveness is the extent to which the changes in the fair value or the cash flows of the hedging instrument are greater or less than those on the hedged item.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The gain (loss) on the change in fair value of the hedging instrument used as a basis for recognising hedge ineffectiveness. Hedge ineffectiveness is the extent to which the changes in the fair value or the cash flows of the hedging instrument are greater or less than those on the hedged item.

+ References

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The gain (loss) recognised in profit or loss on hedge ineffectiveness. [Refer: Gain (loss) on hedge ineffectiveness]

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