Income tax - Unrecognised deferred tax assets (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income tax
Carry forward tax losses	$ 90	$ 102	$ 1,799
Deferred tax assets have not been recognised in respect of the tax losses	$ 14	$ 15	$ 297

The amount of unused tax losses for which no deferred tax asset is recognised in the statement of financial position. [Refer: Unused tax losses [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2022-03-24
-Paragraph 81
-Subparagraph e
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2022-en-r&anchor=para_81_e&doctype=Standard
-URIDate 2022-03-24

Name:	ifrs-full_UnusedTaxLossesForWhichNoDeferredTaxAssetRecognised
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant