Discontinued Operations and Assets Held for Sale (Major Categories of Assets and Liabilities Reflected as Held for Sale) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts receivable	$ 331,859	$ 243,472
Total current assets held for sale	20,947	22,929
Accounts payable	596,071	595,916
Total current liabilities associated with assets held for sale	2,764	3,530
UK Refining And Marketing Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash	17,219	16,631
Accounts receivable	3,728	6,298
Total current assets held for sale	20,947	22,929
Accounts payable	106	837
Refinery decommissioning cost	2,658	2,693
Total current liabilities associated with assets held for sale	$ 2,764	$ 3,530