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Share-based payments - Additional information (Detail) | 12 Months Ended
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Dec. 31, 2018 USD ($) Option Instrument shares | Dec. 31, 2017 USD ($) Option shares
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Percentage of cancellations employees electing to withdraw their investment shares before vesting of their matching shares | 15.00% |
Options outstanding, number of options | Option | 40,114 | 188,766
Aggregate Intrinsic Value Of Outstanding Share Options |  | $ 3,000,000
Liability for cash-settled awards | $ 16,000,000 | $ 15,000,000
Rio Tinto plc [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Percentage of share-based payment charge for plan | 100.00% | 100.00%
Rio Tinto Limited [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Percentage of share-based payment charge for plan | 100.00% | 100.00%
Share Option Plan [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Option expiry period | 2019 |
UK share plan [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Description of method of settlement for share-based payment arrangement | equity |
Performance share plans [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Description of method of settlement for share-based payment arrangement | equity-settled |
Information on how the fair value of share options granted was measured | Monte Carlo simulation model |
Description of award granted for share-based payment arrangement | One-third of the awards granted from 2013 to 2017 (inclusive) are subject to an earnings margin performance target relative to ten global mining comparators. |
Number of global mining comparators | Instrument | 10 |
Percentage of forfeitures, prior to vesting, on outstanding awards | 5.00% | 5.00%
Share-based payments, fair value measurement description | As this is a non-market related performance condition, under IFRS 2, the fair value recognised is reviewed at each accounting date based on the directors’ expectations for the proportion vesting. |
Vesting requirements for share based awards | Forfeitures prior to vesting are assumed at 5% per annum of outstanding awards (2017: 5% per annum). |
Performance share plans [member] | Rio Tinto plc [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Cash-settled awards outstanding | shares | 40,365 |
Liability for cash-settled awards | $ 11,000,000 |
Performance share plans [member] | Rio Tinto plc [member] | Top of range [Member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Cash-settled awards outstanding | shares |  | 26,590
Liability for cash-settled awards |  | $ 9,000,000
Performance share plans [member] | Rio Tinto Limited [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Cash-settled awards outstanding | shares | 276,722 | 276,722
Management share plans [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Description of method of settlement for share-based payment arrangement | equity |
Percentage of forfeitures, prior to vesting, on outstanding awards | 7.00% | 7.00%
Vesting requirements for share based awards | The vesting of these awards is dependent on service conditions being met. |
Bonus deferral plans [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Description of method of settlement for share-based payment arrangement | equity |
Percentage of forfeitures, prior to vesting, on outstanding awards | 3.00% | 3.00%
Vesting requirements for share based awards | The vesting of these awards is dependent only on service conditions being met. |
Bonus deferral plans [member] | Executive directors and product group executives [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Vesting requirements for share based awards | 50% of the bonuses |
Bonus deferral plans [member] | Other executives [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Description of method of settlement for share-based payment arrangement | 25% of the bonuses |
Global employee share plans [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Description of method of settlement for share-based payment arrangement | equity |
Percentage of forfeitures, prior to vesting, on outstanding awards | 5.00% | 5.00%
Vesting requirements for share based awards | The vesting of these matching awards is dependent on service conditions being met and the continued holding of investment shares by the participant until vesting. |
Share Incentive Plans |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Liability for cash-settled awards | $ 5,000,000 |
Share Incentive Plans | Top of range [Member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Liability for cash-settled awards |  | $ 6,000,000
Share Incentive Plans | Rio Tinto plc [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Cash-settled awards outstanding | shares | 46,543 | 33,443
Share Incentive Plans | Rio Tinto Limited [member] |  |
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items] |  |
Cash-settled awards outstanding | shares | 83,092 | 87,019

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- Definition The amount of liabilities arising from share-based payment transactions. Share-based payment transactions are transactions in which the entity: (a) receives goods or services from the supplier of those goods or services (including an employee) in a share-based payment arrangement; or (b) incurs an obligation to settle the transaction with the supplier in a share-based payment arrangement when another group entity receives those goods or services. [Refer: Share-based payment arrangements [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2017-01-01 -Paragraph 51 -Subparagraph b -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_51_b_i&doctype=Standard -URIDate 2017-03-09 + Details
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