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Goodwill - Additional information (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Richards Bay Minerals [member] |  |
Disclosure of reconciliation of changes in goodwill [Line Items] |  |
Impairment charges | $ 0 | $ 0
Fair value less costs of disposal, post-tax discount rate | 8.80% | 8.70%
Description of valuation techniques used to measure fair value less costs of disposal | The recoverable amount has been assessed by reference to FVLCD, in line with the policy set out in note 1(i) and classified as level 3 under the fair value hierarchy. FVLCD was determined by estimating cash flows until the end of the life-of-mine plan including anticipated expansions. In arriving at FVLCD, a post-tax discount rate of 8.8% (2017: 8.7%) has been applied to the post-tax cash flows expressed in real terms. |
Description of level of fair value hierarchy within which fair value measurement is categorized | level 3 |
Description of basis on which recoverable amount determined | Other assumptions include the long-term pig iron and zircon prices and operating costs. Future selling prices and operating costs have been estimated in line with the policy set out in note 1(i). The recoverable amount of the CGU exceeds the carrying value when each of these sensitivities are applied whilst keeping all other assumptions constant. |
Pilbara [member] |  |
Disclosure of reconciliation of changes in goodwill [Line Items] |  |
Fair value less costs of disposal, post-tax discount rate | 6.80% | 6.70%
Description of valuation techniques used to measure fair value less costs of disposal | The annual impairment review of the Pilbara CGU has been assessed by reference to FVLCD using discounted cash flows, which is in line with the policy set out in note 1(i) and is classified as level 3 under the fair value hierarchy. In arriving at FVLCD, a post-tax discount rate of 6.8% (2017: 6.7%) has been applied to the post-tax cash flows expressed in real terms. The recoverable amount was determined to be significantly in excess of carrying value, and there are no reasonably possible changes in key assumptions that would cause the remaining goodwill to be impaired. |
Description of level of fair value hierarchy within which fair value measurement is categorized | level 3 |

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- Definition The description of the basis on which the cash-generating unit's (group of units') recoverable amount has been determined (ie value in use or fair value less costs of disposal). [Refer: Cash-generating units [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2017-01-01 -Paragraph 134 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2017-03-01&anchor=para_134_c&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The description of the level of the fair value hierarchy within which the fair value measurement is categorised in its entirety (without giving regard to the observability of 'costs of disposal') for a cash-generating unit (group of units'). [Refer: Cash-generating units [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2017-01-01 -Paragraph 134 -Subparagraph e -Clause iiA -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2017-03-01&anchor=para_134_e_iiA&doctype=Standard -URIDate 2017-03-09 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2017-01-01 -Paragraph 130 -Subparagraph f -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2017-03-01&anchor=para_130_f_i&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The description of the valuation techniques used to measure fair value less costs of disposal for a cash generating unit (group of units). [Refer: Valuation techniques [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2017-01-01 -Paragraph 134 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2017-03-01&anchor=para_134_e&doctype=Standard -URIDate 2017-03-09 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2017-01-01 -Paragraph 130 -Subparagraph f -Clause ii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2017-03-01&anchor=para_130_f_ii&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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- Definition The discount rate used in the current measurement of fair value less costs of disposal. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2017-01-01 -Paragraph 130 -Subparagraph f -Clause iii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2017-03-01&anchor=para_130_f_iii&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of impairment loss recognised in profit or loss for goodwill. [Refer: Impairment loss recognised in profit or loss; Goodwill] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 3 -IssueDate 2017-01-01 -Paragraph B67 -Subparagraph d -Clause v -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=3&date=2017-03-01&anchor=para_B67_d_v&doctype=Appendix&seq=2 -URIDate 2017-03-09 + Details
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