Condensed Consolidating Financial Statements (Narrative) (Details)	12 Months Ended
Dec. 31, 2019
Consolidating Financial Statements [Abstract]
Percentage of owned subsidiaries guaranteed fixed- and floating-rate notes	100.00%

Percentage Of Owned Subsidiaries Guaranteed Fixed- And Floating-Rate Notes

No definition available.

Name:	gd_PercentageOfOwnedSubsidiariesGuaranteedFixedAndFloatingRateNotes
Namespace Prefix:	gd_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration