Assets Held for Sale and Discontinued Operations (Results of Operations Associated with Discontinued Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Loss) income from discontinued operations	$ (102)	$ (1,267)	$ 106	$ (6,129)
Discontinued Operation | Malaysian Exploration And Production Operations And U.K., U.S. Refining And Marketing Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	246	1	658	4,074
Other costs and expenses (benefits)	348	1,268	552	10,203
(Loss) income before taxes	(102)	(1,267)	106	(6,129)
Income tax expense	0	0	0	0
(Loss) income from discontinued operations	$ (102)	$ (1,267)	$ 106	$ (6,129)
Discontinued operations, held-for-sale or disposed of by sale | King's Quay Floating Production System
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total current assets associated with assets held for sale					$ 250,100