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Financial instruments and risk management - Summary of maximum credit risk exposure of the Group's financial assets (Detail) - Credit risk [Member] - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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Disclosure Of Credit Risk Exposure [Line Items] |  |
Maximum credit risk exposure | $ 14,993 | $ 12,273
Cash and cash equivalents [member] |  |
Disclosure Of Credit Risk Exposure [Line Items] |  |
Maximum credit risk exposure | 10,550 | 8,201
Trade and other receivables [member] |  |
Disclosure Of Credit Risk Exposure [Line Items] |  |
Maximum credit risk exposure | 2,985 | 3,047
Derivative assets [member] |  |
Disclosure Of Credit Risk Exposure [Line Items] |  |
Maximum credit risk exposure | 267 | 532
Loans to equity accounted units [member] |  |
Disclosure Of Credit Risk Exposure [Line Items] |  |
Maximum credit risk exposure | 39 | 39
Fair value [member] | Loans And Receivables [Member] | Held to maturity assets [member] | Investments [member] |  |
Disclosure Of Credit Risk Exposure [Line Items] |  |
Maximum credit risk exposure | $ 1,152 | $ 454

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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 that best represents the maximum exposure to credit risk without taking into account any collateral held or other credit enhancements (for example, netting agreements that do not qualify for offset in accordance with IAS 32). [Refer: Credit risk [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Note Effective 2018-01-01 -Name IFRS -Number 7 -IssueDate 2016-01-13 -Paragraph 35K -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2016-03-30&anchor=para_35K_a&doctype=Standard -URIDate 2016-03-31 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Note Expiry date 2018-01-01 -Name IFRS -Number 7 -IssueDate 2016-01-13 -Paragraph 36 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2016-03-30&anchor=para_36_a&doctype=Standard -URIDate 2016-03-31 + Details
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