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Changes in the Standardised Measure (Detail) - USD ($) $ in Millions | 12 Months Ended
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Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2017
Extractive Industries [Abstract] |  |  |
Standardised measure at the beginning of the year | $ 10,240 | $ 8,242 | $ 8,987
Revisions: |  |  |
Prices, net of production costs | 3,821 | 5,540 | (96)
Changes in future development costs | (228) | (358) | 275
Revisions of reserves quantity estimates | 1,268 | (166) | 2,961
Accretion of discount | 1,178 | 1,016 | 1,147
Changes in production timing and other | (618) | 946 | (1,611)
Revisions | 15,661 | 15,220 | 11,663
Sales of oil and gas, net of production costs | (5,029) | (5,091) | (4,301)
Acquisitions of reserves-in-place | 0 | 0 | 0
Sales of reserves-in-place | (1,489) | (26) | (15)
Previously estimated development costs incurred | 545 | 1,068 | 718
Extensions, discoveries, and improved recoveries, net of future costs | (33) | 502 | (401)
Changes in future income taxes | (503) | (1,433) | 578
Standardised measure at the end of the year | $ 9,152 | $ 10,240 | $ 8,242

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- Definition Amount of increase (decrease) in standardized measure of discounted future net cash flow as a result of change in the estimated future income tax on future pretax net cash flows related to the entity's proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Form 20-F -Section Item 18 -Subsection Instruction 2 + Details
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