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, 2025	Dec. 31, 2024	Dec. 31, 2023
Parent Company Statement of Profit/(Loss) and Other Comprehensive Income [Line Items]
Gains/(losses) on cash flow hedges, related tax	$ (14)	$ 11	$ 0
Parent Company
Parent Company Statement of Profit/(Loss) and Other Comprehensive Income [Line Items]
Gains/(losses) on cash flow hedges, related tax	$ (2)	$ 2	$ 1

The amount of income tax relating to amounts recognised in other comprehensive income in relation to cash flow hedges. [Refer: Cash flow hedges [member]; Other comprehensive income]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2025-01-01
-Paragraph 81
-Subparagraph ab
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-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 90
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_90&doctype=Standard
-URIDate 2025-03-27

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