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Number of Crude Oil and Natural Gas Wells Drilled and Completed (Parenthetical) (Detail) - Wells
 12 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2018
Disclosure of net productive wells and dry wells drilled [line items]      
Net development wells, Productive 1 34 85
Net development wells, Dry 1   1
Net exploratory wells 2 7 2
United States [member]      
Disclosure of net productive wells and dry wells drilled [line items]      
Net development wells, Productive 0 33 84
Net development wells, Dry 1   1
Net exploratory wells 0 1 2
Discontinued operations - Onshore US Cash Generating Units [member] | United States [member]      
Disclosure of net productive wells and dry wells drilled [line items]      
Net development wells, Productive 0 33 84
Net development wells, Dry 0 0 1
Net exploratory wells 0 0 0