Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities (Fair Value of Derivative Instruments) (Details)

v3.4.0.3
Derivative Instruments and Hedging Activities (Fair Value of Derivative Instruments) (Details) - Not Designated as Hedging Instrument [Member] - USD ($)
$ in Thousands
Mar. 31, 2016
Dec. 31, 2015
Derivatives, Fair Value [Line Items]    
Asset Fair Value $ 15,585 $ 19,943
Liability Fair Value (4,290)  
Net Derivative Fair Value 11,295 19,943
Non-Current Liabilities Fair Market Value Of Derivatives [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (3,602)  
Non-Current Liabilities Fair Market Value Of Derivatives [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (3,602)  
Current assets - Fair market value of derivatives [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 15,585 19,943
Current assets - Fair market value of derivatives [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 15,096 19,943
Current assets - Fair market value of derivatives [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 489  
Current liabilities - Fair value of derivatives [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (688)  
Current liabilities - Fair value of derivatives [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (688)  
Balance Sheet Current [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value 14,408 $ 19,943
Balance Sheet Current [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value 489  
Balance Sheet Non Current [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value $ (3,602)