Assets Held for Sale and Discontinued Operations - Major Categories of Assets and Liabilities Reflected as Held for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current liabilities
Total current liabilities associated with assets held for sale	$ 14,372	$ 13,298
Discontinued Operations, Held-for-sale or Disposed of by Sale | Brunei Exploration and Production Operations and UK Refining and Market Operations
Current assets
Cash		25,185
Accounts receivable		4,834
Inventories		406
Prepaid expenses and other		1,882
Property, plant, and equipment, net		82,116
Deferred income taxes and other assets		9,441
Total current assets associated with assets held for sale		123,864
Current liabilities
Accounts payable		3,702
Other accrued liabilities		0
Current maturities of long-term debt (finance lease)		705
Taxes payable		1,411
Asset retirement obligation		240
Long-term debt (finance lease)		7,240
Total current liabilities associated with assets held for sale		$ 13,298
Discontinued Operations, Held-for-sale or Disposed of by Sale | King's Quay Floating Production System and El Dorado Office Building
Current assets
Cash	10,185
Accounts receivable	0
Inventories	406
Prepaid expenses and other	0
Property, plant, and equipment, net	307,704
Deferred income taxes and other assets	9,441
Total current assets associated with assets held for sale	327,736
Current liabilities
Accounts payable	5,306
Other accrued liabilities	45
Current maturities of long-term debt (finance lease)	737
Taxes payable	1,510
Asset retirement obligation	261
Long-term debt (finance lease)	6,513
Total current liabilities associated with assets held for sale	$ 14,372