Inventories (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Inventories
Finished products	$ 2,797	$ 2,219
Work in progress	690	648
Consumable inventory	956	1,059
Total	4,443	3,926
Reversal (provision) for net realizable value	$ 4	$ (86)	$ (199)

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A classification of current inventory representing the amount of goods that have completed the production process and are held for sale in the ordinary course of business. [Refer: Inventories]

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The amount of current inventories. [Refer: Inventories]

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The amount of expense recognised related to the write-down of inventories to net realisable value. [Refer: Inventories]

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A classification of current inventory representing the amount of interchangeable parts that are kept in an inventory and are used for the repair or replacement of failed parts. [Refer: Inventories]

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A classification of current inventory representing the amount of assets currently in production, which require further processes to be converted into finished goods or services. [Refer: Current finished goods; Inventories]

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