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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-06-11</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001247392</rptOwnerCik>
            <rptOwnerName>VAN BOKHORST WILLEM</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>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, Par Value $.01 Per Share</value>
            </securityTitle>
            <transactionDate>
                <value>2020-06-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10183</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>66819</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The grant consists of restricted stock units that shall become vested with respect to 3,394 shares on June 11, 2021, 3,394 shares on May 31, 2022 and 3,395 shares on May 31, 2023, subject to the Participant's continuous service as a Director with the Company through the applicable vesting date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Willem van Bokhorst</signatureName>
        <signatureDate>2020-06-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
