Inventories (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 01, 2017
Inventory, Net [Abstract]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory								$ 214,900
Inventory Valuation Reserves	$ (223,833)				$ (223,833)	$ (332,518)
Lower of cost or market inventory valuation adjustment		$ (84,000)	$ (11,800)	$ 300	$ (108,685)	(291,938)	$ 226,979
Renewable Volume Obligation	$ 27,300					$ 30,500