Changes in Significant Accounting Policies - Reconciliation Of Operating Lease Commitments (Detail) - USD ($) $ in Millions	Jan. 01, 2019	Dec. 31, 2018
Disclosure Of Changes In Sigificant Accounting Policies [abstract]
Operating lease commitments at 31 December 2018 as disclosed under IAS 17		$ 657.4
Discounting	$ (91.0)
Non-lease elements	(356.8)
Lease liability recognised at 1 January 2019	$ 209.6

The amount of liabilities related to the entity's leases. Lease is a contract, or part of a contract, that conveys the right to use an underlying asset for a period of time in exchange for consideration.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2019-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2019-en-r&anchor=para_47_b&doctype=Standard
-URIDate 2019-03-27

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