Investments - Investments in subsidiaries (Detail) - Rio Tinto plc [member] - United Kingdom [member]	12 Months Ended
Dec. 31, 2017
Rio tinto international holdings limited [member]
Disclosure Of Investments In Subsidiaries Joint Ventures And Associates [Abstract]
Company of operation, Subsidiary	Rio Tinto International Holdings Limited
Principal activities, Subsidiary	Holding company
Country of incorporation, Subsidiary	UK
Ownership percentage in subsidiary	100.00%
Rio tinto european holdings limited [member]
Disclosure Of Investments In Subsidiaries Joint Ventures And Associates [Abstract]
Company of operation, Subsidiary	Rio Tinto European Holdings Limited
Principal activities, Subsidiary	Holding company
Country of incorporation, Subsidiary	UK
Ownership percentage in subsidiary	100.00%

The country in which a subsidiary of the entity is incorporated. [Refer: Subsidiaries [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2016-01-13
-Paragraph 16
-Subparagraph b
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2016-03-30&anchor=para_16_b_ii&doctype=Standard
-URIDate 2016-03-31

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2016-01-13
-Paragraph 17
-Subparagraph b
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2016-03-30&anchor=para_17_b_ii&doctype=Standard
-URIDate 2016-03-31

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2016-01-13
-Paragraph 12
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2016-03-30&anchor=para_12_b&doctype=Standard
-URIDate 2016-03-31

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2016-01-13
-Paragraph 19B
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2016-03-30&anchor=para_19B_b&doctype=Standard
-URIDate 2016-03-31

+ Details

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

- Definition

The description of the nature of the entity's operations and principal activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 138
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_138_b&doctype=Standard
-URIDate 2016-03-31

+ Details

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

- Definition

The name of a subsidiary. [Refer: Subsidiaries [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2016-01-13
-Paragraph 17
-Subparagraph b
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2016-03-30&anchor=para_17_b_i&doctype=Standard
-URIDate 2016-03-31

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2016-01-13
-Paragraph 16
-Subparagraph b
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2016-03-30&anchor=para_16_b_i&doctype=Standard
-URIDate 2016-03-31

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2016-01-13
-Paragraph 12
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2016-03-30&anchor=para_12_a&doctype=Standard
-URIDate 2016-03-31

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2016-01-13
-Paragraph 19B
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2016-03-30&anchor=para_19B_a&doctype=Standard
-URIDate 2016-03-31

+ Details

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

- Definition

The proportion of ownership interest in a subsidiary attributable to the entity. [Refer: Subsidiaries [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2016-01-13
-Paragraph 17
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2016-03-30&anchor=para_17_b_iii&doctype=Standard
-URIDate 2016-03-31

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2016-01-13
-Paragraph 16
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2016-03-30&anchor=para_16_b_iii&doctype=Standard
-URIDate 2016-03-31

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2016-01-13
-Paragraph 19B
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2016-03-30&anchor=para_19B_c&doctype=Standard
-URIDate 2016-03-31

+ Details

Name:	ifrs-full_ProportionOfOwnershipInterestInSubsidiary
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Disclosure of investments in subsidiaries joint ventures and associates.

+ References

No definition available.

+ Details

Name:	rio_DisclosureOfInvestmentsInSubsidiariesJointVenturesAndAssociatesAbstract
Namespace Prefix:	rio_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=rio_RioTintoPlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=rio_RioTintoInternationalHoldingsLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=country_GB
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=rio_RioTintoEuropeanHoldingsLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: