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Other reserves and retained earnings - Summary of other reserves and retained earnings (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure Of Other Reserves And Retained Earnings [Line Items] |  |  |  |
Beginning balance | $ 9,216 |  |  |
Change in equity interest held by Rio Tinto |  | $ (165) | [1] | $ 3
Companies no longer consolidated | (2) | 8 |  | 5
Ending balance | 12,284 | 9,216 |  |
Parent and subsidiaries currency translation and exchange adjustments | (70) | 90 |  |
Beginning balance | 21,631 |  |  |
Tax relating to components of other comprehensive income | (153) | 33 |  | (178)
Share buy-back | (2,397) |  |  |
Dividends (note 11) | (4,653) | (3,077) |  | (4,391)
Employee share options and other IFRS 2 charges to the income statement | 98 | 125 |  | 134
Ending balance | 23,761 | 21,631 |  |
Capital redemption reserve [Member] |  |  |  |
Disclosure Of Other Reserves And Retained Earnings [Line Items] |  |  |  |
Beginning balance | 34 | 34 |  | 28
Own shares purchased and cancelled | 4 |  |  | 6
Ending balance | 38 | 34 |  | 34
Hedging reserves [member] |  |  |  |
Disclosure Of Other Reserves And Retained Earnings [Line Items] |  |  |  |
Beginning balance | 32 |  |  | 12
Parent and subsidiaries' net cash flow hedge fair value gains/(losses) | 62 | (88) |  | (41)
Parent and subsidiaries' net cash flow hedge (gains)/losses transferred to the income statement | (62) | 116 |  | 32
Tax on the above |  | 4 |  | (3)
Ending balance | 32 | 32 |  |
Available for sale revaluation reserves [member] |  |  |  |
Disclosure Of Other Reserves And Retained Earnings [Line Items] |  |  |  |
Beginning balance | (126) | (139) |  | (130)
Gains/(losses) on available for sale securities | 19 | 13 |  | (16)
Losses on available for sale securities transferred to the income statement | 6 |  |  | 7
Tax on the above | (1) |  |  |
Transfers and other movements | 122 |  |  |
Ending balance | 20 | (126) |  | (139)
Other reserves [member] |  |  |  |
Disclosure Of Other Reserves And Retained Earnings [Line Items] |  |  |  |
Beginning balance | 11,861 | 11,735 |  | 11,704
Change in equity interest held by Rio Tinto |  | 108 |  |
Own shares purchased from Rio Tinto Limited shareholders to satisfy share options | (64) | (43) |  | (25)
Employee share options: value of services | 31 | 58 |  | 58
Deferred tax on share options | 10 | 3 |  | (2)
Companies no longer consolidated | (124) |  |  |
Ending balance | 11,714 | 11,861 |  | 11,735
Foreign currency translation reserve [member] |  |  |  |
Disclosure Of Other Reserves And Retained Earnings [Line Items] |  |  |  |
Beginning balance | 9,216 | 9,139 |  |
Ending balance | 12,284 | 9,216 |  | 9,139
Beginning balance | (2,585) | (2,491) |  | (492)
Parent and subsidiaries currency translation and exchange adjustments | 2,942 | (204) |  | (1,940)
Equity accounted units currency translation adjustments | 34 | 11 |  | (57)
Currency translation reclassified on disposal | 78 | 99 |  | (2)
Transfers and other movements | 11 |  |  |
Ending balance | 480 | (2,585) |  | (2,491)
Retained earnings [Member] |  |  |  |
Disclosure Of Other Reserves And Retained Earnings [Line Items] |  |  |  |
Change in equity interest held by Rio Tinto | 43 | 40 | [1] | 20
Own shares purchased from Rio Tinto Limited shareholders to satisfy share options | (133) |  |  |
Companies no longer consolidated | 130 |  |  |
Beginning balance | 21,631 | 19,736 |  | 26,110
Parent and subsidiaries' profit/(loss) for the year | 8,423 | 4,298 |  | (1,218)
Equity accounted units' profit after tax for the year | 339 | 319 |  | 352
Actuarial gains/(losses) | 1 | (94) |  | 616
Tax relating to components of other comprehensive income | (150) | 30 |  | (173)
Total comprehensive income/(loss) for the year | 8,613 | 4,553 |  | (423)
Share buy-back | (2,312) |  |  | (1,946)
Dividends (note 11) | (4,250) | (2,725) |  | (4,076)
Companies no longer consolidated | 130 |  |  |
Own shares purchased/treasury shares reissued for share options and other movements | (18) | (37) |  | (27)
Employee share options and other IFRS 2 charges to the income statement | 57 | 64 |  | 78
Transfer and other movements | (133) |  |  |
Ending balance | $ 23,761 | $ 21,631 |  | $ 19,736
[1] | The restructure of Coal & Allied Industries Limited completed on 3 February 2016. The restructure involved the exchange of a 32.4 per cent interest in Hunter Valley Operations mine for an additional 20 per cent shareholding in Coal & Allied Industries Limited, increasing Rio Tinto’s shareholding of Coal & Allied Industries Limited from 80 per cent to 100 per cent. Rio Tinto sold its 100 per cent interest in Coal & Allied Industries Limited on 1 September 2017.

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- Definition Adjustments for undistributed profits of investments accounted for using the equity method to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Investments accounted for using equity method; Profit (loss)] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 7 -IssueDate 2016-01-13 -Paragraph 20 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2016-03-30&anchor=para_20&doctype=Standard -URIDate 2016-03-31 + Details
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- Definition A component of equity representing the entity's cumulative undistributed earnings or deficit. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Name IAS -Number 1 -IssueDate 2016-01-13 -Paragraph 78 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_78_e&doctype=Standard -URIDate 2016-03-31 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Name IAS -Number 1 -IssueDate 2016-01-13 -Paragraph IG6 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_IG6&doctype=Implementation%20Guidance -URIDate 2016-03-31 + Details
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- Definition This represents increases to non-controlling interests where interests in subsidiaries are disposed of such that the entity holding no longer qualifies for consolidation. + References No definition available. + Details
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- Definition Companies no longer consolidated retained earnings. + References No definition available. + Details
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