Trade and other payables - Additional Information (Detail) $ in Millions	Dec. 31, 2020 USD ($)
UK Portfolio [member]
Statement [Line Items]
Rent payable	$ 65

Amounts payable that the entity does not separately disclose in the same statement or note.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_55&doctype=Standard
-URIDate 2020-01-01

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant