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Summary Of Significant Accounting Policies Discontinued Operations (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Axle Business [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Loss on Disposition of Business $ 146us-gaap_GainLossOnSaleOfBusiness
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= gd_AxleBusinessMember		  
Termination Of A-12 Program    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Loss Related to Litigation Settlement   129us-gaap_GainLossRelatedToLitigationSettlement
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= gd_TerminationOf12ProgramMember
Litigation Settlement, Amount   $ 198us-gaap_LitigationSettlementAmount
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= gd_TerminationOf12ProgramMember