Pension and Other Post-retirement Obligations - Summary of Net Liability Recognised in Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Jun. 30, 2017
Defined benefit pension schemes/post-employment obligations [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Fair value of defined benefit scheme assets	$ (633)	$ (687)
Scheme deficit	257	234
Unrecognised surplus	0	0
Unrecognised past service credits	0	0
Adjustment for employer contributions tax	0	0
Net liability recognised in the Consolidated Balance Sheet	257	234
Defined benefit pension schemes/post-employment obligations [member] \| Funded defined benefit obligation [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Present value of defined benefit obligation	616	665
Defined benefit pension schemes/post-employment obligations [member] \| Unfunded defined benefit obligation [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Present value of defined benefit obligation	274	256
Post-retirement medical schemes [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Scheme deficit	192	204
Unrecognised surplus	0	0
Unrecognised past service credits	0	0
Adjustment for employer contributions tax	0	0
Net liability recognised in the Consolidated Balance Sheet	192	204
Post-retirement medical schemes [member] \| Unfunded defined benefit obligation [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Present value of defined benefit obligation	$ 192	$ 204

Defined benefit obligation adjustment for employer contributions tax.

No definition available.

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Namespace Prefix:	bhp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Defined benefit obligation unrecognized past service credits.

+ References

No definition available.

+ Details

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Namespace Prefix:	bhp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Defined benefit obligation unrecognized surplus.

+ References

No definition available.

+ Details

Name:	bhp_DefinedBenefitObligationUnrecognizedSurplus
Namespace Prefix:	bhp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The present value, without deducting any plan assets, of expected future payments required to settle the obligation resulting from employee service in the current and prior periods. [Refer: Plan assets, at fair value]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 57
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_57_a&doctype=Standard
-URIDate 2017-03-09

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

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

- Definition

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 140
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_140_a&doctype=Standard
-URIDate 2017-03-09

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]]

+ References

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The present value of the defined benefit obligation, less the fair value of the plan assets (if any). [Refer: Plan assets [member]]

+ References

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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- Details

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Period Type: