Investments in joint ventures - Transactions between group and its joint ventures (Details) - Joint ventures - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Sales to joint ventures
Sales to related parties	$ 2,974	$ 4,884	$ 4,603
Related party receivable	180	431	251
Purchases from joint ventures
Purchases of goods, related party	959	1,812	1,336
Related party payables	$ 84	$ 225	$ 300

Purchases from joint ventures [Abstract]

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Sales To Joint Ventures [Abstract]

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The amounts payable resulting from related party transactions. [Refer: Related parties [member]]

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The amounts receivable resulting from related party transactions. [Refer: Related parties [member]]

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The amount of goods purchased by the entity in related party transactions. [Refer: Related parties [member]]

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The amount of revenue arising from the sale of goods in related party transactions. [Refer: Revenue; Related parties [member]]

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