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Inventories - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Classes Of Inventories [Line Items]
Inventory write-downs, net of reversals	$ 48
Net inventory write- back		$ 7
Inventory partly write offs		74
Disclosure - Inventories - Additional information (Detail) [Line Items]
Inventories pledged as security for liabilities	$ 566	611
Previously Stated [Member]
Classes Of Inventories [Line Items]
Net inventory write- back		$ 81

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- Definition

The decrease in financial assets resulting from write-off. [Refer: Financial assets]

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The amount recognised as a reduction in the amount of inventories recognised as an expense due to the reversal of any write-down of inventories resulting from an increase in net realisable value. [Refer: Inventories; Inventory write-down]

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