Inventories (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Inventory [Line Items]
Inventory valuation adjustment	$ 0	$ 2,590	$ 5,667
Crude Supply and Logistics [Member] | Crude Oil [Member]
Inventory [Line Items]
Inventory valuation adjustment		$ 2,600