Derivative Instruments (Fair Market Value of Derivative Instruments Included on the Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Liability	$ 7,402	$ 16,067
[PrepaidExpensesAndOtherCurrentAssetsMember]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Net	0	1,247
[NondesignatedMember] \| [OtherLiabilitiesMember]
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Liability	(7,402)	(16,067)
[NondesignatedMember] \| [OilAndGasCommodityDerivativesMember] \| [PrepaidExpensesAndOtherCurrentAssetsMember]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Net	$ 0	$ 1,247

Fair value as of the balance sheet date of the embedded derivative or group of embedded derivatives classified as a liability.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44B

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 12-16, 44A, 44B

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44A

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44A, 44B

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details