Dividends - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of dividends paid and proposed [line items]
Final Proposed (not recognised as a liability at 31 December)		$ 85.9	$ 78.1
Payments for dividends		$ 721	$ 199
Proposed dividends [member]
Disclosure of dividends paid and proposed [line items]
Payments for dividends	$ 150

The amount, per share, of dividends proposed or declared before financial statements were authorised for issue but not recognised as distribution to owners.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 137
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_137_a&doctype=Standard
-URIDate 2020-01-01

Name:	ifrs-full_DividendsProposedOrDeclaredBeforeFinancialStatementsAuthorisedForIssueButNotRecognisedAsDistributionToOwnersPerShare
Namespace Prefix:	ifrs-full_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration