Derivative Instruments and Hedging Activities (Derivatives Fair Value by Balance Sheet Location) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Net Derivative Fair Value	$ 5,472	$ 26,601
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Fair Value	7,094	27,850
Liability Fair Value	(1,622)	(1,249)
Net Derivative Fair Value	5,472	26,601
Current assets - Fair market value of derivatives [Member] \| Not Designated as Hedging Instrument [Member] \| Crude Oil [Member]
Derivatives, Fair Value [Line Items]
Asset Fair Value	6,218	26,588
Current assets - Fair market value of derivatives [Member] \| Not Designated as Hedging Instrument [Member] \| Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Asset Fair Value	671	1,262
Current liabilities - Fair market value of derivatives [Member] \| Not Designated as Hedging Instrument [Member] \| Crude Oil [Member]
Derivatives, Fair Value [Line Items]
Liability Fair Value	(1,621)	(1,242)
Current liabilities - Fair market value of derivatives [Member] \| Not Designated as Hedging Instrument [Member] \| Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Liability Fair Value	(1)	(7)
Non-current assets - Other long-term assets [Member] \| Not Designated as Hedging Instrument [Member] \| Crude Oil [Member]
Derivatives, Fair Value [Line Items]
Asset Fair Value	205
Balance Sheet Current [Member] \| Not Designated as Hedging Instrument [Member] \| Crude Oil [Member]
Derivatives, Fair Value [Line Items]
Net Derivative Fair Value	4,597	25,346
Balance Sheet Current [Member] \| Not Designated as Hedging Instrument [Member] \| Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Net Derivative Fair Value	670	$ 1,255
Balance Sheet Non Current [Member] \| Not Designated as Hedging Instrument [Member] \| Crude Oil [Member]
Derivatives, Fair Value [Line Items]
Net Derivative Fair Value	$ 205

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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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.

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