Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified
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3 Months Ended |
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Mar. 31, 2015
Impaired_Asset_And_Liability
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Mar. 31, 2014
Impaired_Asset_And_Liability
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Dec. 31, 2014
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Assets |
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|
|
Deferred compensation plan |
$ 13,322us-gaap_DeferredCompensationPlanAssets |
|
$ 13,115us-gaap_DeferredCompensationPlanAssets |
Derivative contracts |
134,041us-gaap_DerivativeFairValueOfDerivativeAsset |
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137,603us-gaap_DerivativeFairValueOfDerivativeAsset |
Total assets |
147,363us-gaap_AssetsFairValueDisclosure |
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150,718us-gaap_AssetsFairValueDisclosure |
Liabilities |
|
|
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Deferred compensation plan |
29,096us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent |
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28,932us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent |
Total liabilities |
29,096us-gaap_LiabilitiesFairValueDisclosure |
|
28,932us-gaap_LiabilitiesFairValueDisclosure |
Number of non-financial assets and liabilities impaired |
0cog_NumberOfNonFinancialAssetsAndLiabilitiesImpaired |
0cog_NumberOfNonFinancialAssetsAndLiabilitiesImpaired |
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Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring basis |
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|
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Assets |
|
|
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Deferred compensation plan |
13,322us-gaap_DeferredCompensationPlanAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
13,115us-gaap_DeferredCompensationPlanAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Derivative contracts |
0us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
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0us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Total assets |
13,322us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
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13,115us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Liabilities |
|
|
|
Deferred compensation plan |
29,096us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
28,932us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Total liabilities |
29,096us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
28,932us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Significant Other Observable Inputs (Level 2) | Recurring basis |
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|
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Assets |
|
|
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Deferred compensation plan |
0us-gaap_DeferredCompensationPlanAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
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0us-gaap_DeferredCompensationPlanAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Derivative contracts |
50,716us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
51,645us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Total assets |
50,716us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
51,645us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Liabilities |
|
|
|
Deferred compensation plan |
0us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
0us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Total liabilities |
0us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
0us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Significant Unobservable Inputs (Level 3) | Recurring basis |
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|
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Assets |
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|
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Deferred compensation plan |
0us-gaap_DeferredCompensationPlanAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
0us-gaap_DeferredCompensationPlanAssets / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Derivative contracts |
83,325us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
85,958us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Total assets |
83,325us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
85,958us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Liabilities |
|
|
|
Deferred compensation plan |
0us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
|
0us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Total liabilities |
$ 0us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
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$ 0us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |