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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-02-06</periodOfReport>

    <issuer>
        <issuerCik>0001593538</issuerCik>
        <issuerName>NAVIENT CORP</issuerName>
        <issuerTradingSymbol>NAVI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001710338</rptOwnerCik>
            <rptOwnerName>HAUBER STEPHEN M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>123 S. JUSTISON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WILMINGTON</rptOwnerCity>
            <rptOwnerState>DE</rptOwnerState>
            <rptOwnerZipCode>19801</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>SVP, Chief Risk&amp;Compliance Off</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-02-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>559</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.76</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>87534.6241</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On February 6, 2017, the reporting person was granted 4,521 restricted stock units (&quot;RSUs&quot;) under the Navient Corporation 2014 Omnibus Incentive Plan representing the right to receive shares of Navient Corporation (&quot;Navient&quot;) common stock in the future, which vest in one-third increments on each of the first, second and third anniversaries of the grant. On February 6, 2018, 1,507 shares of such RSUs were settled and an additional 68 shares were issued to the reporting person upon the vesting of the related dividend equivalent rights.  In connection with this settlement, 559 shares were withheld by Navient, as approved by the Navient Compensation and Personnel Committee (the &quot;Committee&quot;), to satisfy the reporting person's tax withholding obligations.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Kurt T. Slawson (POA) for Stephen M. Hauber</signatureName>
        <signatureDate>2018-02-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
