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Contracts In Process - Cost Of Contracts (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Contracts In Process [Line Items]    
Contract costs and estimated profits $ 7,494gd_ContractCostsAndEstimatedProfits $ 7,961gd_ContractCostsAndEstimatedProfits
Other contract costs 1,064gd_OtherContractCosts 1,178gd_OtherContractCosts
Costs in excess of billings on uncompleted contracts or programs, total 8,558us-gaap_CostsInExcessOfBillingsOnUncompletedContractsOrPrograms 9,139us-gaap_CostsInExcessOfBillingsOnUncompletedContractsOrPrograms
Advances and progress payments (3,967)us-gaap_CustomerAdvancesAndProgressPaymentsForLongTermContractsOrPrograms (4,359)us-gaap_CustomerAdvancesAndProgressPaymentsForLongTermContractsOrPrograms
Total contracts in process 4,591gd_ContractsInProcess 4,780gd_ContractsInProcess
Percent of contracts-in-process not expected to be billed in 2015 15.00%gd_PercentOfContractsInProcessYearEndBalanceNotExpectedToBeBilledInNextTwelveMonths  
Canadian Maritime Helicopter Project (MHP)    
Contracts In Process [Line Items]    
Contracts-in-process not expected to bill in 2015 220us-gaap_UnbilledReceivablesNotBillableAtBalanceSheetDate
/ gd_ContractsInProcessAxis
= gd_CanadianMaritimeHelicopterProjectMhpMember		  
Decrease in Unbilled Receivables $ 80us-gaap_IncreaseDecreaseInUnbilledReceivables
/ gd_ContractsInProcessAxis
= gd_CanadianMaritimeHelicopterProjectMhpMember