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Goodwill - Summary of Allocated goodwill (Detail) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
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Disclosure of reconciliation of changes in goodwill [Line Items] |  |  |
Goodwill | $ 1,037 | $ 951 | $ 892
Richards Bay Minerals [member] |  |  |
Disclosure of reconciliation of changes in goodwill [Line Items] |  |  |
Goodwill | 552 | 502 |
Pilbara [member] |  |  |
Disclosure of reconciliation of changes in goodwill [Line Items] |  |  |
Goodwill | 389 | 360 |
Dampier Salt [member] |  |  |
Disclosure of reconciliation of changes in goodwill [Line Items] |  |  |
Goodwill | $ 96 | $ 89 |

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