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Condensed Consolidating Financial Statements - Narrative (Details) | 6 Months Ended
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Jul. 01, 2018
Consolidating Financial Statements [Abstract] |
Percentage of owned subsidiaries (the guarantors) | 100.00%

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- Definition Consolidating Financial Statements [Abstract] + References No definition available. + Details
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- Definition Percentage Of Owned Subsidiaries Guaranteed Fixed Rate Notes + References No definition available. + Details
Name: | gd_PercentageOfOwnedSubsidiariesGuaranteedFixedRateNotes
Namespace Prefix: | gd_
Data Type: | num:percentItemType
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Period Type: | duration