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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-02-07</periodOfReport>

    <issuer>
        <issuerCik>0000024741</issuerCik>
        <issuerName>CORNING INC /NY</issuerName>
        <issuerTradingSymbol>GLW</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001508144</rptOwnerCik>
            <rptOwnerName>STEVERSON LEWIS A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE RIVERFRONT PLAZA</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CORNING</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>14831</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>EVP and CLAO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

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        <derivativeTransaction>
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            <transactionTimeliness></transactionTimeliness>
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                    <value>11745</value>
                </transactionShares>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
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                </underlyingSecurityShares>
            </underlyingSecurity>
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        <derivativeTransaction>
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                <transactionPricePerShare>
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                </transactionShares>
                <transactionPricePerShare>
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                <underlyingSecurityShares>
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        <derivativeTransaction>
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                <value>Performance Share Unit</value>
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                <transactionCode>M</transactionCode>
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            <transactionTimeliness></transactionTimeliness>
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                <transactionShares>
                    <value>352</value>
                </transactionShares>
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                    <value>0</value>
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                <footnoteId id="F8"/>
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                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>352</value>
                </underlyingSecurityShares>
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                    <value>32450</value>
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    <footnotes>
        <footnote id="F1">Each performance share unit represents a contingent right to receive one share of Corning Incorporated common stock.</footnote>
        <footnote id="F2">Performance share units (PSUs) were earned February 7, 2024 per Compensation Committee decision that performance criteria were satisfied for fiscal year 2023 pursuant to the 2023 agreement. Earned PSUs remain restricted until April 15, 2026, when they vest and convert to common stock, subject to service-based vesting requirement.</footnote>
        <footnote id="F3">Performance share units (PSUs) were earned February 7, 2024 per Compensation Committee decision that performance criteria were satisfied for fiscal year 2023 pursuant to the 2023 agreement. Earned PSUs remain restricted until vesting.  The earned units will vest 1/3 after 1 year from the February 8, 2023 grant date and 1/6 every 6 months thereafter until fully vested on the third anniversary of the grant date.</footnote>
        <footnote id="F4">Performance share units (PSUs) were earned February 7, 2024 per Compensation Committee decision that performance criteria were satisfied for fiscal year 2023 pursuant to the 2022 agreement. Earned PSUs remain restricted until April 15, 2025, when they vest and convert to common stock, subject to service-based vesting requirement.</footnote>
        <footnote id="F5">Performance share units (PSUs) were earned February 7, 2024 per Compensation Committee decision that performance criteria were satisfied for fiscal year 2023 pursuant to the 2021 agreement. Earned PSUs remain restricted until April 15, 2024, when they vest and convert to common stock, subject to service-based vesting requirement.</footnote>
        <footnote id="F6">Vesting to satisfy tax requirement pursuant to the 2023 agreement.</footnote>
        <footnote id="F7">Vesting to satisfy tax requirement pursuant to the 2022 agreement.</footnote>
        <footnote id="F8">Vesting to satisfy tax requirement pursuant to the 2021 agreement.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Linda E. Jolly, Power of Attorney</signatureName>
        <signatureDate>2024-02-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
