Annual report pursuant to Section 13 and 15(d)

Derivatives And Fair Value (Derivative Instruments Accounted For At Fair Value On A Recurring Basis) (Details)

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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