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Deferred Taxation - Recognised and unrecognised amounts in deferred tax assets (Parenthetical) (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items] |  |
Deferred tax assets | $ 3,395 | $ 3,728
Deferred tax loss recovery period | 6 years |
Unrecognised deferred tax assets | $ 3,676 | 3,442
Realised or unrealised capital losses [member] |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items] |  |
Deferred tax assets | $ 250 | 105
Deferred tax loss recovery period | 1 year |
Unrecognised deferred tax assets | $ 777 | 964
Mongolia [Member] |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items] |  |
Deferred tax assets | 631 | 441
Unrecognised deferred tax assets | 61 |
Mongolia [Member] | Tax losses [member] |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items] |  |
Deferred tax assets | $ 432 | $ 365
Deferred tax loss recovery period | 8 years |

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- Definition The amounts of income taxes recoverable in future periods in respect of: (a) deductible temporary differences; (b) the carryforward of unused tax losses; and (c) the carryforward of unused tax credits. [Refer: Temporary differences [member]; Unused tax credits [member]; Unused tax losses [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2016-01-13 -Paragraph 81 -Subparagraph g -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2016-03-30&anchor=para_81_g_i&doctype=Standard -URIDate 2016-03-31 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2016-01-13 -Paragraph 54 -Subparagraph o -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_54_o&doctype=Standard -URIDate 2016-03-31 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2016-01-13 -Paragraph 56 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_56&doctype=Standard -URIDate 2016-03-31 + 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 amount of unused tax losses for which no deferred tax asset is recognised in the statement of financial position. [Refer: Unused tax losses [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2016-01-13 -Paragraph 81 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2016-03-30&anchor=para_81_e&doctype=Standard -URIDate 2016-03-31 + Details
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- Definition Deferred tax loss recovery minimum period. + References No definition available. + Details
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- Details
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- Details
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- Details
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