Income Tax Expense - Summary of Income Tax Recognised in Other Comprehensive Income (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Major components of tax expense (income) [abstract]
Income tax relating to components of other comprehensive income, deferred taxes	$ 15	$ 17	$ 12
Income tax relating to components of other comprehensive income, current taxes	$ 12	$ 5	$ (14)

Deferred income tax relating to components of other comprehensive income.

No definition available.

Name:	bhp_DeferredIncomeTaxRelatingToComponentsOfOtherComprehensiveIncome
Namespace Prefix:	bhp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration