Share-based compensation - Share-based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation	$ 125	$ 123	$ 100
Performance Share Plan expense
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation	123	120	97
Share Option expense
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation	$ 2	$ 3	$ 3