Hedging Program and Derivatives (Summary Position of Derivatives) (Details) - Oil - WTI [Member] - Fixed Swap [Member]	12 Months Ended
Dec. 31, 2017 bbl $ / bbl
2018 [Member]
Derivative [Line Items]
Daily volume (bbl) \| bbl	3,149
Swap price (in usd per bbl) \| $ / bbl	50.38
2019 [Member]
Derivative [Line Items]
Daily volume (bbl) \| bbl	2,200
Swap price (in usd per bbl) \| $ / bbl	55.27

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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