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Ceiling Test Write-down (Details)
12 Months Ended
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
$ / mcf
$ / bbl
$ / Mcfe
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]      
Rate for discounting future cash flows 10.00%    
Ceiling test write-down $ 0 $ 0 $ 40,304,000
Mcf of natural gas      
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]      
Average sales prices (usd per unit) | $ / mcf     2.51
Barrel of oil      
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]      
Average sales prices (usd per unit) | $ / bbl     40.85
Mcfe of natural gas liquids      
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]      
Average sales prices (usd per unit) | $ / Mcfe     1.82
Cash Flow Hedging | Commodity Contract      
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]      
Ceiling test write-downs decrease     $ 8,000,000