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Retirement Benefits (Details 8)
 12 Months Ended
Dec. 31, 2014
Domestic Equity Securities  
Plan Asset Allocation Ranges (Table Amounts) [Abstract]  
Asset allocation ranges, minimum 13.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= noc_DomesticEquitySecuritiesMember
Asset allocation ranges, maximum 33.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= noc_DomesticEquitySecuritiesMember
International equities  
Plan Asset Allocation Ranges (Table Amounts) [Abstract]  
Asset allocation ranges, minimum 7.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= noc_InternationalEquitySecuritiesMember
Asset allocation ranges, maximum 27.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= noc_InternationalEquitySecuritiesMember
Fixed Income Securities  
Plan Asset Allocation Ranges (Table Amounts) [Abstract]  
Asset allocation ranges, minimum 30.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_FixedIncomeSecuritiesMember
Asset allocation ranges, maximum 50.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_FixedIncomeSecuritiesMember
Alternative Investments  
Plan Asset Allocation Ranges (Table Amounts) [Abstract]  
Asset allocation ranges, minimum 10.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= noc_RealEstateAndOtherSecuritiesMember
Asset allocation ranges, maximum 30.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= noc_RealEstateAndOtherSecuritiesMember