XML 54 R56.htm IDEA: XBRL DOCUMENT v2.4.1.9
Fair Value Measurements (Textuals) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended 3 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Mar. 31, 2014
Dec. 31, 2011
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value   $ (26)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue $ (151)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue   $ (103)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Liability Value (384)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue        
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Investment Income   (16)us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss 82us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss    
Money Market Funds, at Carrying Value 1us-gaap_MoneyMarketFundsAtCarryingValue 2us-gaap_MoneyMarketFundsAtCarryingValue      
Deferred Compensation Plan Assets 9us-gaap_DeferredCompensationPlanAssets 8us-gaap_DeferredCompensationPlanAssets      
Assets, Fair Value Disclosure 618us-gaap_AssetsFairValueDisclosure 5us-gaap_AssetsFairValueDisclosure      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings (419)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 (90)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 135us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss 10us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss 4us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales 39us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements 45us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements 45us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements 91us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3    
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) (373)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss        
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3 3us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3    
Obligations, Fair Value Disclosure (15)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations (16)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations      
Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Gross Of Tax   6nfx_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentGrossOfTax      
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax   4us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForWritedownOfSecuritiesNetOfTax      
Swap [Member]          
Derivative Assets 994us-gaap_DerivativeAssets
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Derivative Liability   (28)us-gaap_DerivativeLiabilities
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Auction Rate Securities [Member]          
Available-for-sale Securities, Fair Value Disclosure   39us-gaap_AvailableForSaleSecurities
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Proceeds from Sale of Available-for-sale Securities 39us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities
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    39us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities
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Commodity Option [Member]          
Derivative Liability (381)us-gaap_DerivativeLiabilities
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(8)us-gaap_DerivativeLiabilities
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Equity Securities [Member]          
Available-for-sale Securities, Fair Value Disclosure 10us-gaap_AvailableForSaleSecurities
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8us-gaap_AvailableForSaleSecurities
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= us-gaap_EquitySecuritiesMember
     
Oil contracts [Member]          
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value 510us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue
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Oil contracts [Member] | Options Held [Member]          
Derivative Liability, Fair Value, Total (422)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue
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Oil contracts [Member] | Maximum [Member] | Options Held [Member]          
Fair Value Assumptions Expected Volatility Curves 63.41%nfx_FairValueAssumptionsExpectedVolatilityCurves
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/ us-gaap_RangeAxis
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Fair Value Inputs, Entity Credit Risk 1.76%us-gaap_FairValueInputsEntityCreditRisk
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= nfx_OilContractsMember
/ us-gaap_DerivativeByNatureAxis
= us-gaap_OptionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
       
Oil contracts [Member] | Minimum [Member] | Options Held [Member]          
Fair Value Assumptions Expected Volatility Curves 28.03%nfx_FairValueAssumptionsExpectedVolatilityCurves
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Fair Value Inputs, Entity Credit Risk 0.01%us-gaap_FairValueInputsEntityCreditRisk
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/ us-gaap_RangeAxis
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Natural Gas [Member]          
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value 103us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue
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Natural Gas [Member] | Options Held [Member]          
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value 41us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue
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= nfx_NaturalGasContractsMember
/ us-gaap_DerivativeByNatureAxis
= us-gaap_OptionMember
       
Natural Gas [Member] | Maximum [Member] | Options Held [Member]          
Fair Value Assumptions Expected Volatility Curves 60.53%nfx_FairValueAssumptionsExpectedVolatilityCurves
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= nfx_NaturalGasContractsMember
/ us-gaap_DerivativeByNatureAxis
= us-gaap_OptionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
       
Fair Value Inputs, Entity Credit Risk 1.12%us-gaap_FairValueInputsEntityCreditRisk
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= nfx_NaturalGasContractsMember
/ us-gaap_DerivativeByNatureAxis
= us-gaap_OptionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
       
Natural Gas [Member] | Minimum [Member] | Options Held [Member]          
Fair Value Assumptions Expected Volatility Curves 23.11%nfx_FairValueAssumptionsExpectedVolatilityCurves
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= nfx_NaturalGasContractsMember
/ us-gaap_DerivativeByNatureAxis
= us-gaap_OptionMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
       
Fair Value Inputs, Entity Credit Risk 0.01%us-gaap_FairValueInputsEntityCreditRisk
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Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member]          
Money Market Funds, at Carrying Value 1us-gaap_MoneyMarketFundsAtCarryingValue
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2us-gaap_MoneyMarketFundsAtCarryingValue
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Deferred Compensation Plan Assets 9us-gaap_DeferredCompensationPlanAssets
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8us-gaap_DeferredCompensationPlanAssets
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Assets, Fair Value Disclosure 8us-gaap_AssetsFairValueDisclosure
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7us-gaap_AssetsFairValueDisclosure
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Obligations, Fair Value Disclosure (12)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations
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(11)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations
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Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] | Swap [Member]          
Derivative Assets 0us-gaap_DerivativeAssets
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Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] | Auction Rate Securities [Member]          
Available-for-sale Securities, Fair Value Disclosure   0us-gaap_AvailableForSaleSecurities
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Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] | Commodity Option [Member]          
Derivative Assets 0us-gaap_DerivativeAssets
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Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] | Equity Securities [Member]          
Available-for-sale Securities, Fair Value Disclosure 10us-gaap_AvailableForSaleSecurities
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Significant Other Observable Fair Value Inputs (Level 2) [Member]          
Money Market Funds, at Carrying Value 0us-gaap_MoneyMarketFundsAtCarryingValue
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0us-gaap_MoneyMarketFundsAtCarryingValue
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Deferred Compensation Plan Assets 0us-gaap_DeferredCompensationPlanAssets
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0us-gaap_DeferredCompensationPlanAssets
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Assets, Fair Value Disclosure 994us-gaap_AssetsFairValueDisclosure
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Financial and Nonfinancial Liabilities, Fair Value Disclosure   (28)us-gaap_LiabilitiesFairValueDisclosure
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Obligations, Fair Value Disclosure 0us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations
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0us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations
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Significant Other Observable Fair Value Inputs (Level 2) [Member] | Swap [Member]          
Derivative Assets 994us-gaap_DerivativeAssets
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Derivative Liability   (28)us-gaap_DerivativeLiabilities
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Significant Other Observable Fair Value Inputs (Level 2) [Member] | Auction Rate Securities [Member]          
Available-for-sale Securities, Fair Value Disclosure   0us-gaap_AvailableForSaleSecurities
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Significant Other Observable Fair Value Inputs (Level 2) [Member] | Commodity Option [Member]          
Derivative Assets 0us-gaap_DerivativeAssets
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0us-gaap_DerivativeAssets
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Significant Other Observable Fair Value Inputs (Level 2) [Member] | Equity Securities [Member]          
Available-for-sale Securities, Fair Value Disclosure 0us-gaap_AvailableForSaleSecurities
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Fair Value, Inputs, Level 3 [Member]          
Liability Value (384)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
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Money Market Funds, at Carrying Value 0us-gaap_MoneyMarketFundsAtCarryingValue
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0us-gaap_MoneyMarketFundsAtCarryingValue
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Deferred Compensation Plan Assets 0us-gaap_DeferredCompensationPlanAssets
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0us-gaap_DeferredCompensationPlanAssets
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Assets, Fair Value Disclosure   26us-gaap_AssetsFairValueDisclosure
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Obligations, Fair Value Disclosure (3)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations
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(5)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisObligations
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Fair Value, Inputs, Level 3 [Member] | Swap [Member]          
Derivative Assets 0us-gaap_DerivativeAssets
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0us-gaap_DerivativeAssets
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Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member]          
Available-for-sale Securities, Fair Value Disclosure   39us-gaap_AvailableForSaleSecurities
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Fair Value, Inputs, Level 3 [Member] | Commodity Option [Member]          
Derivative Liability (381)us-gaap_DerivativeLiabilities
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(8)us-gaap_DerivativeLiabilities
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Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member]          
Available-for-sale Securities, Fair Value Disclosure 0us-gaap_AvailableForSaleSecurities
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Derivative Financial Instruments, Assets [Member]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value     (115)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Liability Value   (8)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
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Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Investment Income     82us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings   (66)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements   57us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
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Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)   (10)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
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Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3 3us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
   
Investments [Member]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
(39)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
(36)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
  (32)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Investment Income 0us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
(6)us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
0us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
(6)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
10us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
4us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales 39us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
       
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InvestmentsMember
   
6.875% Senior Subordinated Notes due 2020 [Member]          
Debt Instrument, Fair Value Disclosure 721us-gaap_DebtInstrumentFairValue
/ us-gaap_DebtInstrumentAxis
= nfx_SeniorSubordinatedNotesDue2020Member
755us-gaap_DebtInstrumentFairValue
/ us-gaap_DebtInstrumentAxis
= nfx_SeniorSubordinatedNotesDue2020Member
     
7.125% Senior Subordinated Notes due 2018 [Member]          
Debt Instrument, Fair Value Disclosure 0us-gaap_DebtInstrumentFairValue
/ us-gaap_DebtInstrumentAxis
= nfx_SeniorSubordinatedNotesDue2018Member
624us-gaap_DebtInstrumentFairValue
/ us-gaap_DebtInstrumentAxis
= nfx_SeniorSubordinatedNotesDue2018Member
     
5.625% Senior Notes Due 2024 [Member]          
Debt Instrument, Fair Value Disclosure 989us-gaap_DebtInstrumentFairValue
/ us-gaap_DebtInstrumentAxis
= nfx_SeniorNotesDue2024Member
1,025us-gaap_DebtInstrumentFairValue
/ us-gaap_DebtInstrumentAxis
= nfx_SeniorNotesDue2024Member
     
5.75 %Senior Notes Due 2022 [Member]          
Debt Instrument, Fair Value Disclosure 772us-gaap_DebtInstrumentFairValue
/ us-gaap_DebtInstrumentAxis
= nfx_SeniorNotesDue2022Member
767us-gaap_DebtInstrumentFairValue
/ us-gaap_DebtInstrumentAxis
= nfx_SeniorNotesDue2022Member
     
Stockholder Value Appreciation Program [Member]          
Liability Value (3)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= nfx_StockholderValueAppreciationProgramMember
       
Derivative Financial Instruments, Assets [Member]          
Liability Value (381)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
       
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings (381)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
       
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
       
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements 5us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
       
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) (375)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
       
Stock Compensation Plan [Member]          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value     0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByLiabilityClassAxis
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  0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
Liability Value (3)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
(5)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
     
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Investment Income     0us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings (38)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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= us-gaap_StockCompensationPlanMember
(18)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByLiabilityClassAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
       
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements     0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
   
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements 40us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
13us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
     
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) 2us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
0us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
     
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3 $ 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
$ 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
$ 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByLiabilityClassAxis
= us-gaap_StockCompensationPlanMember
   
Implied [Member] | Stockholder Value Appreciation Program [Member]          
SBC Expected Volatility Rate, Maximum 50.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
/ us-gaap_FairValueByLiabilityClassAxis
= nfx_StockholderValueAppreciationProgramMember
/ nfx_VolatilityTypeAxis
= nfx_HistoricalMember