Quarterly report pursuant to Section 13 or 15(d)

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

v3.5.0.2
Derivative Instruments and Hedging Activities (Fair Value of Derivative Instruments) (Details) - Not Designated as Hedging Instrument [Member] - USD ($)
$ in Thousands
Sep. 30, 2016
Dec. 31, 2015
Derivatives, Fair Value [Line Items]    
Asset Fair Value $ 3,559 $ 19,943
Liability Fair Value (10,722)  
Net Derivative Fair Value (7,163) 19,943
Non-Current Assets Fair Market Value Of Derivatives [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 54  
Non-Current Assets Fair Market Value Of Derivatives [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 3  
Non-current liabilities - Fair value of derivatives [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (2,936)  
Non-current liabilities - Fair value of derivatives [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (2,936)  
Current assets - Fair value of derivatives [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 3,502 19,943
Current assets - Fair value of derivatives [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 3,473 19,943
Current assets - Fair value of derivatives [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 29  
Current liabilities - Fair value of derivatives [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (7,786)  
Current liabilities - Fair value of derivatives [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (7,553)  
Current liabilities - Fair value of derivatives [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (233)  
Balance Sheet Current [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value (4,080) $ 19,943
Balance Sheet Current [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value (204)  
Balance Sheet Non Current [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value (2,882)  
Balance Sheet Non Current [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value $ 3