Annual report pursuant to Section 13 and 15(d)

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

v3.6.0.2
Derivative Instruments and Hedging Activities (Fair Value of Derivative Instruments) (Details) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Derivatives, Fair Value [Line Items]    
Asset Fair Value $ 103 $ 19,943
Liability Fair Value (18,296)  
Net Derivative Fair Value (18,193) 19,943
Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 103 19,943
Liability Fair Value (18,296)  
Net Derivative Fair Value (18,193) 19,943
Non-current liabilities - Fair value of derivatives [Member] | Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (28)  
Non-current liabilities - Fair value of derivatives [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (28)  
Current assets - Fair value of derivatives [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 103 19,943
Current liabilities - Fair value of derivatives [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (17,675)  
Current liabilities - Fair value of derivatives [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (593)  
Balance Sheet Current [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value (17,572) $ 19,943
Balance Sheet Current [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value (593)  
Balance Sheet Non Current [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value $ (28)