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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, 2019
Jun. 30, 2018
Jun. 30, 2017
Costs incurred oil and gas property acquisition exploration and development activities [line items]      
Acquisitions of proved property $ 0 $ 0 $ 0
Acquisitions of unproved property 5 9 74
Exploration 726 734 738
Development 978 1,777 1,412
Total costs 1,709 2,520 2,224
Australia [member]      
Costs incurred oil and gas property acquisition exploration and development activities [line items]      
Acquisitions of proved property 0 0 0
Exploration 44 25 32
Development 132 195 360
Total costs 176 220 392
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 5 9 12
Exploration 190 418 471
Development 792 1,548 1,034
Total costs 987 1,975 1,517
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     62
Exploration 492 291 235
Development 54 34 18
Total costs $ 546 $ 325 $ 315