Inventories (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Inventory Disclosure - Narrative [Abstract]
Inventory Valuation Reserves	$ 175,593				$ 175,593		$ 360,138
Lower of cost or market inventory valuation adjustment	$ 47,801	$ (106,926)			$ (184,545)	$ (210,764)
Cost of Sales Reduction		$ 25,300	$ 33,800	$ 37,900