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: