Discontinued Operations and Assets Held for Sale (Major Categories of Assets and Liabilities Reflected as Held for Sale) (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts receivable		$ 357,099	$ 522,672	[1]
Total current assets held for sale		27,070	38,340	[1]
Accounts payable		784,975	1,529,848	[1]
Total current liabilities associated with assets held for sale		2,776	7,297	[1]
Asset retirement obligation - Seal asset		681,528	793,474	[1]
Total non-current liabilities associated with assets held for sale	[2]	85,900
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash		4,126	7,927
Accounts receivable		22,944	29,358
Other			1,055
Total current assets held for sale		27,070	38,340
Accounts payable		270	2,433
Accrued compensation and severance			2,179
Refinery decommissioning cost		2,506	2,685
Total current liabilities associated with assets held for sale		2,776	$ 7,297
Asset retirement obligation - Seal asset		85,900
Total non-current liabilities associated with assets held for sale		$ 85,900

[1] Reclassified to conform to current presentation. See Note B for additional information.

[2] Liabilities held for sale related to Seal properties in Canada which were sold in January 2017.