Derivatives And Fair Value (Derivative Instruments Accounted For At Fair Value On A Recurring Basis) (Details) - Commodity Contract [Member] - Not Designated as Hedging Instrument [Member] - Prepayments and other [Member] $ in Thousands	Dec. 31, 2016 USD ($)
Derivatives, Fair Value [Line Items]
Derivative instruments	$ 1,227
Fair Value, Inputs, Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments	$ 1,227