Business and Non-Current Asset Disposals - Summary of Business and Non-Current Asset Disposals (Parenthetical) (Detail) $ in Billions	12 Months Ended
Dec. 31, 2019 USD ($)
CRH [Member]
Disclosure of Joint Venture Divestment [Abstract]
Percentage Sale of Group	50.00%
MHIL [Member]
Disclosure of Joint Venture Divestment [Abstract]
Deferred Proceeds Arising From Divestment	$ 0.3

The proportion of ownership interest in a joint venture attributable to the entity. [Refer: Joint ventures [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Number 27
-IssueDate 2021-01-01
-Paragraph 17
-Subparagraph b
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-URIDate 2021-03-24

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2021-01-01
-Paragraph 16
-Subparagraph b
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2021-01-01
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-Subparagraph a
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Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration