Condensed parent company financial information - Condensed Parent Company statement of profit/(loss) and other comprehensive income (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Parent Company Statement of Profit/(Loss) and Other Comprehensive Income [Line Items]
(Losses)/gains on cash flow hedges, including related tax	$ 0	$ 1	$ (2)
Parent Company [member]
Parent Company Statement of Profit/(Loss) and Other Comprehensive Income [Line Items]
(Losses)/gains on cash flow hedges, including related tax	$ 2	$ 1	$ (2)

The amount of income tax relating to amounts recognised in other comprehensive income in relation to investments in equity instruments that the entity has designated at fair value through other comprehensive income applying paragraph 5.7.5 of IFRS 9. [Refer: Other comprehensive income; Reserve of gains and losses from investments in equity instruments]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 90
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_90&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2024-01-01
-Paragraph 81
-Subparagraph ab
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2024-en-r&anchor=para_81_ab&doctype=Standard
-URIDate 2024-03-27

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Balance Type:	debit
Period Type:	duration