<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-06-15</periodOfReport>

    <issuer>
        <issuerCik>0000821002</issuerCik>
        <issuerName>G III APPAREL GROUP LTD /DE/</issuerName>
        <issuerTradingSymbol>GIII</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001332749</rptOwnerCik>
            <rptOwnerName>Aaron Sammy</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O G-III APPAREL GROUP, LTD.</rptOwnerStreet1>
            <rptOwnerStreet2>512 SEVENTH AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10018</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <officerTitle>Vice Chairman and President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, Par Value $.01 Per Share</value>
            </securityTitle>
            <transactionDate>
                <value>2020-06-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>29008</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.04</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>563507</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, Par Value $.01 Per Share</value>
            </securityTitle>
            <transactionDate>
                <value>2020-06-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>14609</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.13</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>548898</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The reported price represents the weighted average price for shares sold in multiple transactions ranging from $13.75 to $14.33 to satisfy the Reporting Person's tax obligations in connection with the vesting of restricted stock units. The details of the amounts and prices will be provided to the Issuer, any shareholders of the Issuer or the SEC on request.</footnote>
        <footnote id="F2">The reported price represents the weighted average price for shares sold in multiple transactions ranging from $14.64 to $15.41 to satisfy the Reporting Person's tax obligations in connection with the vesting of restricted stock units. The details of the amounts and prices will be provided to the Issuer, any shareholders of the Issuer or the SEC on request.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Sammy Aaron</signatureName>
        <signatureDate>2020-06-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
