Debt - Additional Information (Detail) $ in Millions	3 Months Ended
Apr. 03, 2016 USD ($)
Debt Instrument [Line Items]
Commercial Paper	$ 0.0
Percentage of owned subsidiaries guaranteed	100.00%
Commercial Paper
Debt Instrument [Line Items]
Percentage of owned subsidiaries guaranteed	100.00%
Line of Credit Facility, Remaining Borrowing Capacity	$ 2,000.0
Multi-Year Facility Expiring July 2018 \| Commercial Paper
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	1,000.0
Multi-year Facility Expiring November 2020 \| Commercial Paper
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 1,000.0

Percentage Of Owned Subsidiaries Guaranteed Fixed Rate Notes

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- Definition

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a)(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13)(2))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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Balance Type:	credit
Period Type:	instant

- Details

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- Details

Name:	us-gaap_LongtermDebtTypeAxis=gd_MultiYearFacilityExpiringJulyTwoThousandEighteenMember
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- Details

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