Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.3
Derivative Instruments and Hedging Activities (Fair Value of Derivative Instruments) (Details) - Not Designated as Hedging Instrument - USD ($)
$ in Thousands
Sep. 30, 2019
Dec. 31, 2018
Derivatives, Fair Value [Line Items]    
Asset Fair Value $ 36,241 $ 65,114
Liability Fair Value (11,514) (17,920)
Net Derivative Fair Value 24,727 47,194
Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 24,916 65,114
Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (8,941) (10,480)
Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 3,736  
Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (2,573) (7,440)
Commodity - Oil | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 23,487 60,097
Commodity - Oil | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (8,795) (10,480)
Commodity - Oil | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value 14,692 49,617
Commodity - Oil | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 3,736 0
Commodity - Oil | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (2,233) (5,672)
Commodity - Oil | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value 1,503 (5,672)
Commodity - Natural gas | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 1,429 5,017
Commodity - Natural gas | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (146) 0
Commodity - Natural gas | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value 1,283 5,017
Commodity - Natural gas | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 0 0
Commodity - Natural gas | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Liability Fair Value (340) (1,768)
Commodity - Natural gas | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value (340) $ (1,768)
Contingent consideration arrangement | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 116  
Contingent consideration arrangement | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Liability Fair Value 0  
Contingent consideration arrangement | Fair value of derivatives - Current    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value 116  
Contingent consideration arrangement | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Asset Fair Value 7,473  
Contingent consideration arrangement | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Liability Fair Value 0  
Contingent consideration arrangement | Fair value of derivatives - Non-current    
Derivatives, Fair Value [Line Items]    
Net Derivative Fair Value $ 7,473