Leases - Narrative (Detail) - I F R S16 - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of initial application of standards or interpretations [Line Items]
Lease commitments, not commenced	$ 125	$ 119
Leases expiring in 12 months or fewer	$ 155	$ 108

The amount of the lease commitments for short-term leases accounted for applying paragraph 6 of IFRS 16. Short-term lease is a lease that, at the commencement date, has a lease term of 12 months or less. A lease that contains a purchase option is not a short-term lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2020-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2020-en-r&anchor=para_55&doctype=Standard
-URIDate 2020-01-01

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