XML 273 R266.htm IDEA: XBRL DOCUMENT v3.8.0.1

Post-retirement benefits - Results summary of sensitivity analysis (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Actuarial assumption of discount rates [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of discount rates [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of expected rates of inflation [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of expected rates of inflation [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of expected rates of salary increases [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of expected rates of salary increases [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of allowance for future improvements in longevity [member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase in actuarial assumption of longevity trend	1 year	1 year
Decrease in actuarial assumption of longevity trend	1 year	1 year
Actuarial assumption of allowance for future improvements in longevity [member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase in actuarial assumption of longevity trend	1 year	1 year
Decrease in actuarial assumption of longevity trend	1 year	1 year
Actuarial assumption of medical cost trend rates [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	1.00%	1.00%
Decrease of percentage points	1.00%	1.00%
Actuarial assumption of medical cost trend rates [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	1.00%	1.00%
Decrease of percentage points	1.00%	1.00%

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_DisclosureOfSensitivityAnalysisForActuarialAssumptionsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The reasonably possible percentage of the decrease in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2016-01-13
-Paragraph 145
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_145_a&doctype=Standard
-URIDate 2016-03-31

+ Details

Name:	ifrs-full_PercentageOfReasonablyPossibleDecreaseInActuarialAssumption
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The reasonably possible percentage of the increase in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2016-01-13
-Paragraph 145
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_145_a&doctype=Standard
-URIDate 2016-03-31

+ Details

Name:	ifrs-full_PercentageOfReasonablyPossibleIncreaseInActuarialAssumption
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Decrease In Actuarial Assumption Of Longevity Trend Rates

+ References

No definition available.

+ Details

Name:	rio_DecreaseInActuarialAssumptionOfLongevityTrendRates
Namespace Prefix:	rio_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Increase In Actuarial Assumption Of Longevity Trend Rates

+ References

No definition available.

+ Details

Name:	rio_IncreaseInActuarialAssumptionOfLongevityTrendRates
Namespace Prefix:	rio_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	ifrs-full_ActuarialAssumptionsAxis=ifrs-full_ActuarialAssumptionOfDiscountRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=rio_PensionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=rio_OtherRetirementBenefitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_ActuarialAssumptionsAxis=ifrs-full_ActuarialAssumptionOfExpectedRatesOfInflationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_ActuarialAssumptionsAxis=ifrs-full_ActuarialAssumptionOfExpectedRatesOfSalaryIncreasesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_ActuarialAssumptionsAxis=rio_ActuarialAssumptionOfAllowanceForFutureImprovementsInLongevityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_ActuarialAssumptionsAxis=ifrs-full_ActuarialAssumptionOfMedicalCostTrendRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: