Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities (Derivatives Fair Value by Balance Sheet Location) (Details)

v3.3.0.814
Derivative Instruments and Hedging Activities (Derivatives Fair Value by Balance Sheet Location) (Details) - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value $ 18,966 $ 26,601
Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 18,966 27,850
Liability Fair Value   (1,249)
Net Derivative Fair Value 18,966 26,601
Non-Current Assets Fair Market Value Of Derivatives [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 2,203  
Current assets - Fair market value of derivatives [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 16,356 26,588
Current assets - Fair market value of derivatives [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 407 1,262
Current liabilities - Fair market value of derivatives [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value   (1,242)
Current liabilities - Fair market value of derivatives [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Liability Fair Value   (7)
Balance Sheet Current [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value 16,356 25,346
Balance Sheet Current [Member] | Not Designated as Hedging Instrument [Member] | Natural Gas [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value 407 $ 1,255
Balance Sheet Non Current [Member] | Not Designated as Hedging Instrument [Member] | Crude Oil [Member]    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value $ 2,203