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Ageing of Capitalised Exploratory Well Costs (Detail)
$ in Millions
Jun. 30, 2020
USD ($)
Project
Jun. 30, 2019
USD ($)
Project
Jun. 30, 2018
USD ($)
Project
Jun. 30, 2017
USD ($)
Extractive Industries [Abstract]        
Exploratory well costs capitalised for a period of one year or less $ 120 $ 210 $ 124  
Exploratory well costs capitalised for a period greater than one year 969 830 670  
At the end of the year $ 1,089 $ 1,040 $ 794 $ 668
Number of projects that have been capitalised for a period greater than one year | Project 14 13 17