The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period.

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The amount of exploratory well costs that have been capitalized for a period of greater than one year after the completion of drilling.

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The expense recorded to reduce the value of oil and gas assets consisting of proved properties and unproved properties as the estimate of future successful production from these properties is reduced.

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The cash inflow to dispose of long-lived, physical assets and mineral interests in oil and gas properties used for normal oil and gas operations.

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Property, Plant and Equipment (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended
	Mar. 17, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Well costs		$ 182,401	$ 178,433	$ 181,616	$ 217,326
Exploratory well costs capitalized more than one year		182,400
Impairment of oil and gas Properties		171,296	967,530
Proceeds from sale of oil and gas property and equipment	$ 267,700
Vietnam
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year		90,600
United States
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year		45,900
Impairment of oil and gas Properties		0	927,821
Brunei
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year		25,700
MEXICO
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year		15,400
Canada
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year		4,800
Impairment of oil and gas Properties		$ 171,296	$ 0