Derivatives (Schedule Of Fair Value Of Derivative Assets And Liabilities) (Details) - Other Current Assets [Member] - Total Commodity Derivatives [Member] - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Not Designated As Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 850	$ 1,703
Derivative Asset, Fair Value, Gross Liability	(850)	(388)
Derivative Asset	0	1,315
Derivative Liability, Fair Value, Gross Liability	(2,544)	(388)
Derivative Liability, Fair Value, Gross Asset	2,544	388
Derivative Liability	0	0
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	3,882	0
Derivative Asset, Fair Value, Gross Liability	(3,882)	0
Derivative Asset	0	0
Derivative Liability, Fair Value, Gross Liability	(8,342)	(23)
Derivative Liability, Fair Value, Gross Asset	8,342	23
Derivative Liability	$ 0	$ 0