XML 260 R253.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Post-retirement benefits - Summary of maturity of defined benefit obligations (Detail) - yr | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of defined benefit plans [Line Items] |  |  |
Proportion relating to current employees | 20.00% | 21.00% | 22.00%
Proportion relating to former employees not yet retired | 11.00% | 12.00% | 11.00%
Proportion relating to retirees | 69.00% | 67.00% | 67.00%
Defined benefit obligation | 100.00% | 100.00% | 100.00%
Average duration of obligations (years) | 13.9 | 14.3 | 13.4
Pension benefits [member] |  |  |
Disclosure of defined benefit plans [Line Items] |  |  |
Proportion relating to current employees | 20.00% |  |
Proportion relating to former employees not yet retired | 12.00% |  |
Proportion relating to retirees | 68.00% |  |
Defined benefit obligation | 100.00% |  |
Average duration of obligations (years) | 14.0 |  |
Other Benefits [member] |  |  |
Disclosure of defined benefit plans [Line Items] |  |  |
Proportion relating to current employees | 16.00% |  |
Proportion relating to former employees not yet retired | 1.00% |  |
Proportion relating to retirees | 83.00% |  |
Defined benefit obligation | 100.00% |  |
Average duration of obligations (years) | 12.7 |  |

X
- 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
Name: | ifrs-full_DisclosureOfDefinedBenefitPlansLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average duration of a defined benefit obligation. [Refer: Weighted average [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2016-01-13 -Paragraph 147 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_147_c&doctype=Standard -URIDate 2016-03-31 + Details
Name: | ifrs-full_WeightedAverageDurationOfDefinedBenefitObligation
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined benefit obligation maturity percentage. + References No definition available. + Details
Name: | rio_DefinedBenefitObligationMaturityPercentage
Namespace Prefix: | rio_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined benefit obligations relating to current employees maturity percentage. + References No definition available. + Details
Name: | rio_DefinedBenefitObligationsRelatingToCurrentEmployeesMaturityPercentage
Namespace Prefix: | rio_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined benefit obligations relating to former employees not yet retired maturity percentage. + References No definition available. + Details
Name: | rio_DefinedBenefitObligationsRelatingToFormerEmployeesNotYetRetiredMaturityPercentage
Namespace Prefix: | rio_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined benefit obligations relating to retirees maturity percentage. + References No definition available. + Details
Name: | rio_DefinedBenefitObligationsRelatingToRetireesMaturityPercentage
Namespace Prefix: | rio_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | ifrs-full_DefinedBenefitPlansAxis=rio_DefinedBenefitPensionPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_DefinedBenefitPlansAxis=rio_OtherDefinedBenefitPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |