Investment in Associates and Joint Ventures - Summary of Investments in Associates and Joint Ventures (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Disclosure of associates and joint ventures [line items]
Derivative financial instruments	$ (13)	$ (19)
Option contract [member]
Disclosure of associates and joint ventures [line items]
Derivative financial instruments	(4)
Joint ventures [member]
Disclosure of associates and joint ventures [line items]
Charge for the year	$ 23

The amount of financial assets classified as derivative instruments. [Refer: Financial assets; Derivatives [member]]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

The amount recognised as a reduction of the carrying amount of an asset or cash-generating unit to its recoverable amount. [Refer: Carrying amount [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information about associate and joint ventures associated with domain members defined in one or many axes of the table.

+ References

No definition available.

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