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Number of Productive Crude Oil and Natural Gas Wells in which we Held an Interest (Parenthetical) (Detail)	Jun. 30, 2018 Wells
Productive wells [Line Items]
Crude oil wells, Gross	1,411
Crude oil wells, Net	747
Natural gas wells, Gross	6,831
Natural gas wells, Net	2,068
United States [member]
Productive wells [Line Items]
Crude oil wells, Gross	998
Crude oil wells, Net	547
Natural gas wells, Gross	6,660
Natural gas wells, Net	2,012
United States [member] | Discontinued Operations - Onshore US Cash Generating Units [Member]
Productive wells [Line Items]
Crude oil wells, Gross	971
Crude oil wells, Net	536
Natural gas wells, Gross	6,660
Natural gas wells, Net	2,012

X

- Definition

The total number of producing gas wells and gas wells capable of production, in which the entity owns an undivided working interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1208
-Paragraph (a)

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- Definition

The total number of producing gas wells and gas wells capable of production, in which the entity owns a fractional working interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1208
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The total number of producing oil wells and oil wells capable of production, in which the entity owns an undivided working interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
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+ References

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-Publisher SEC
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