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Intangible assets - Summary of exploration and evaluation expenditure (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Exploration And Evaluation Expenditure [Abstract] |  |  |
Net expenditure in the year (net of cash proceeds of US$233 million (2017: US$3 million; 2016: US$208 million) on disposal of undeveloped projects) | $ 345 | $ 493 | $ 284
Non-cash movements and non-cash proceeds on disposal of undeveloped projects | 45 | (24) | (177)
Amount capitalised during the year | 90 | 57 | 8
Net charge for the year | (210) | (460) | (453)
Reconciliation to income statement |  |  |
Exploration and evaluation costs | (488) | (445) | (497)
Profit/(loss) relating to interests in undeveloped projects | 278 | (15) | 44
Net charge for the year | $ (210) | $ (460) | $ (453)

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- Definition The amount of expense arising from the search for mineral resources, including minerals, oil, natural gas and similar non-regenerative resources after the entity has obtained legal rights to explore in a specific area, as well as the determination of the technical feasibility and commercial viability of extracting the mineral resource. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 6 -IssueDate 2017-01-01 -Paragraph 24 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=6&date=2017-03-01&anchor=para_24_b&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of liabilities arising from the search for mineral resources, including minerals, oil, natural gas and similar non-regenerative resources after the entity has obtained legal rights to explore in a specific area, as well as the determination of the technical feasibility and commercial viability of extracting the mineral resource. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 6 -IssueDate 2017-01-01 -Paragraph 24 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=6&date=2017-03-01&anchor=para_24_b&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The net outflow (cash and non-cash) for the purchase of exploration and evaluation assets. + References No definition available. + Details
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- Definition The net cash outflow for the purchase of exploration and evaluation assets. + References No definition available. + Details
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- Definition Exploration and evaluation expenditure [abstract] + References No definition available. + Details
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- Definition Non-cash movements and non-cash proceeds on disposal of undeveloped projects. + References No definition available. + Details
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- Definition The amount of Profit/(loss) relating to interests in undeveloped projects. + References No definition available. + Details
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- Definition Reconciliation to income statement. + References No definition available. + Details
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