Discontinued Operations (Major Categories of Assets and Liabilities Reflected as Held for Sale) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts receivable	$ 232,558	$ 357,099
Total current assets held for sale	22,245	27,070
Accounts payable	595,775	784,975
Total current liabilities associated with assets held for sale	2,952	2,776
UK Refining And Marketing Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash	13,050	4,126
Accounts receivable	9,195	22,944
Total current assets held for sale	22,245	27,070
Accounts payable	508	270
Refinery decommissioning cost	2,444	2,506
Total current liabilities associated with assets held for sale	$ 2,952	$ 2,776