Annual report pursuant to Section 13 and 15(d)

Derivatives And Fair Value (Effect Of Derivative Instruments On The Condensed Consolidated Statements Of Operations) (Details)

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Derivatives And Fair Value (Effect Of Derivative Instruments On The Condensed Consolidated Statements Of Operations) (Details) - Not Designated as Hedging Instrument [Member] - Other, net [Member] - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Crude Oil Swaps [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Derivative, Gain (Loss) on Derivative, Net $ 4,264    
Crude Oil Puts [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Derivative, Gain (Loss) on Derivative, Net   $ (1,032) $ (1,711)