Fair Value Measurements (Quantitative Information About Unobservable Inputs Used In Level 3) (Details) - WTI Options [Member] - Option Model [Member]	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs Commodity Price Volatility	76.00%	64.00%
Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Inputs Commodity Price Volatility	17.00%	18.00%

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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