Derivatives (Oil Derivative Contracts) (Details) - Oil Derivative Contracts	12 Months Ended
Dec. 31, 2018 $ / bbl bbl
Price Swap Contracts \| 2019
Derivative [Line Items]
Volume in Bbls \| bbl	182,500
Weighted Average Swap Price (USD per unit)	63.03
Price Swap Contracts \| 2019 \| Maximum
Derivative [Line Items]
Swap Price (USD per unit)	63.03
Price Swap Contracts \| 2019 \| Minimum
Derivative [Line Items]
Swap Price (USD per unit)	63.03
Short Call Options \| 2019
Derivative [Line Items]
Volume in Bbls \| bbl	2,701,000
Weighted Average Option Price (USD per unit)	66.31
Short Call Options \| 2019 \| Maximum
Derivative [Line Items]
Option Price (USD per unit)	75.20
Short Call Options \| 2019 \| Minimum
Derivative [Line Items]
Option Price (USD per unit)	56.50
Short Call Options \| 2020
Derivative [Line Items]
Volume in Bbls \| bbl	585,600
Weighted Average Option Price (USD per unit)	64.32
Short Call Options \| 2020 \| Maximum
Derivative [Line Items]
Option Price (USD per unit)	73.80
Short Call Options \| 2020 \| Minimum
Derivative [Line Items]
Option Price (USD per unit)	59.55
Long Put Options \| 2019
Derivative [Line Items]
Volume in Bbls \| bbl	2,883,500
Weighted Average Option Price (USD per unit)	53.80
Long Put Options \| 2019 \| Maximum
Derivative [Line Items]
Option Price (USD per unit)	62.00
Long Put Options \| 2019 \| Minimum
Derivative [Line Items]
Option Price (USD per unit)	50.00
Long Put Options \| 2020
Derivative [Line Items]
Volume in Bbls \| bbl	1,537,200
Weighted Average Option Price (USD per unit)	55.54
Long Put Options \| 2020 \| Maximum
Derivative [Line Items]
Option Price (USD per unit)	62.50
Long Put Options \| 2020 \| Minimum
Derivative [Line Items]
Option Price (USD per unit)	50.00
Short Put Options \| 2019
Derivative [Line Items]
Volume in Bbls \| bbl	2,883,500
Weighted Average Option Price (USD per unit)	42.72
Short Put Options \| 2019 \| Maximum
Derivative [Line Items]
Option Price (USD per unit)	52.00
Short Put Options \| 2019 \| Minimum
Derivative [Line Items]
Option Price (USD per unit)	37.50
Short Put Options \| 2020
Derivative [Line Items]
Volume in Bbls \| bbl	1,537,200
Weighted Average Option Price (USD per unit)	44.64
Short Put Options \| 2020 \| Maximum
Derivative [Line Items]
Option Price (USD per unit)	50.00
Short Put Options \| 2020 \| Minimum
Derivative [Line Items]
Option Price (USD per unit)	37.50

The average strike price on the group of price risk option contracts such as put options or call options.

No definition available.

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- Definition

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.

+ References

No definition available.

+ Details

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- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

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- Definition

The strike price on the price risk option contract such as a put option or a call option.

+ References

No definition available.

+ Details

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- Definition

Average fixed price related to the group of price risk swap derivatives.

+ References

No definition available.

+ Details

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- Definition

Fixed price related to the price risk swap derivative.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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