Derivative Financial Instruments (Derivatives And Hedging-Overall-Subsequent Measurement) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (27,770)	$ (32,586)	$ 71,248
Sales [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(56,338)	(38,584)	68,426
Cost of Sales [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	25,566	10,998	(8,997)
Operating Expenses [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 3,002	$ (5,000)	$ 11,819