Derivatives (Schedule Of Fair Value Of Derivative Assets And Liabilities) (Details) - Other Current Assets [Member] - Total Commodity Derivatives [Member] - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Not Designated As Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 300	$ 1,703
Derivative Asset, Fair Value, Gross Liability	(300)	(388)
Derivative Asset	0	1,315
Derivative Liability, Fair Value, Gross Liability	(1,085)	(388)
Derivative Liability, Fair Value, Gross Asset	1,085	388
Derivative Liability	0	0
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	4,924	0
Derivative Asset, Fair Value, Gross Liability	(4,924)	0
Derivative Asset	0	0
Derivative Liability, Fair Value, Gross Liability	(8,097)	(23)
Derivative Liability, Fair Value, Gross Asset	8,097	23
Derivative Liability	$ 0	$ 0