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Investment in Joint Operations (Details) - Wafi-Golpu joint operation
12 Months Ended
Jun. 30, 2019
Disclosure of joint operations [line items]  
Proportion of ownership interest in joint operation (as a percent) 50.00%
Newcrest Mining Limited  
Disclosure of joint operations [line items]  
Proportion of ownership interest in joint operation (as a percent) 50.00%