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Goodwill - Summary of Allocated goodwill (Detail) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure of reconciliation of changes in goodwill [Line Items]      
Goodwill $ 922 $ 912 $ 1,037
Richards Bay Minerals [Member]      
Disclosure of reconciliation of changes in goodwill [Line Items]      
Goodwill 487 474  
Pilbara [Member]      
Disclosure of reconciliation of changes in goodwill [Line Items]      
Goodwill 349 351  
Dampier Salt [Member]      
Disclosure of reconciliation of changes in goodwill [Line Items]      
Goodwill $ 86 $ 87