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Supplementary Oil And Gas Information (Unaudited) - Oil and Natural Gas Liquids Narrative (Details) - Crude Oil, Synthetic Crude Oil, Bitumen, Natural Gas, Natural Gas Liquids - MMBbls	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reserve Quantities [Line Items]
Change in proved developed and undeveloped reserves, net (in MMbbl)	1,400	625	828
Extensions and discoveries (in MMbbl)	726	364	912
Improved recovery (in MMbbl)	58	181	64
Purchases of reserves in place (in MMbbl)	28	668	16
Sales of reserves in place (in MMbbl)	0	0	4
Production (in MMbbl)	320	285	274
Economic revisions due to prices (in MMbbl)	805	(285)	(51)
Revisions of prior estimates (in MMbbl)	103	(19)	165

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- Definition

Proved Developed And Undeveloped Reserves, Economic Revisions Due To Prices

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Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
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Changes in proved reserve estimates resulting from application of improved recovery techniques.

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Volume increase (decrease) of proved reserves of oil and gas.

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-Publisher SEC
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Production of proved reserves.

+ References

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-Publisher SEC
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Purchase of minerals in place.

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Revisions represent changes in previous estimates of proved reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors.

+ References

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Sales of minerals in place.

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