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Derivatives - Narrative (Details)
bbl in Thousands
9 Months Ended
Sep. 30, 2017
USD ($)
bbl
Jul. 14, 2016
5.00% Convertible Senior Notes due 2021    
Credit Derivatives [Line Items]    
Debt instrument, interest rate 5.00% 5.00%
5.00% Convertible Senior Notes due 2021 | Convertible Debt    
Credit Derivatives [Line Items]    
Debt instrument, interest rate 5.00%  
Options Collar | Over the Counter    
Credit Derivatives [Line Items]    
Derivative contracts, barrels 52  
Option Collars and Swap | Over the Counter    
Credit Derivatives [Line Items]    
Derivative contracts, barrels 75  
Interest Rate Swap    
Credit Derivatives [Line Items]    
Fixed interest rate 1.10%  
Notional amount | $ $ 200,000,000  
Long | Commodity derivatives | Over the Counter    
Credit Derivatives [Line Items]    
Derivative contracts, barrels 305  
Long | Energy Related Derivative | Over the Counter    
Credit Derivatives [Line Items]    
Derivative contracts, barrels 115