Summary Of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Apr. 03, 2016	Apr. 05, 2015
Accounting Policies [Abstract]
Length of fiscal quarters, weeks	91 days
Net increase in operating earnings from the quarterly impact of revisions in contract	$ 104	$ 63
Net increase in operating earnings per share from the quarterly impact of revisions in contract	$ 0.22	$ 0.12

Net Increase decrease in operating earnings per share from quarterly impact of revisions in contract estimates.

No definition available.

Name:	gd_NetIncreaseDecreaseInOperatingEarningsPerShareFromQuarterlyImpactOfRevisionsInContractEstimates
Namespace Prefix:	gd_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration