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Costs Incurred Relating to Oil and Gas Property Acquisition, Exploration and Development Activities (Detail) - USD ($)
$ in Millions
 12 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2018
Costs incurred oil and gas property acquisition exploration and development activities [line items]      
Acquisitions of proved property $ 0 $ 0 $ 0
Acquisitions of unproved property 44 5 9
Exploration 686 726 734
Development 1,008 978 1,777
Total costs 1,738 1,709 2,520
Australia [member]      
Costs incurred oil and gas property acquisition exploration and development activities [line items]      
Acquisitions of proved property 0    
Acquisitions of unproved property 0    
Exploration 38 44 25
Development 232 132 195
Total costs 270 176 220
United States [member]      
Costs incurred oil and gas property acquisition exploration and development activities [line items]      
Acquisitions of proved property 0 0 0
Acquisitions of unproved property 38 5 9
Exploration 278 190 418
Development 676 792 1,548
Total costs 992 987 1,975
Other countries [member]      
Costs incurred oil and gas property acquisition exploration and development activities [line items]      
Acquisitions of proved property 0 0 0
Acquisitions of unproved property 6    
Exploration 370 492 291
Development 100 54 34
Total costs $ 476 $ 546 $ 325