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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-02-28</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>EVP, Chief Risk&amp;Compliance Off</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8294</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>12.22</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>120411.0072</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents performance stock units (&quot;PSUs&quot;) awarded under the Navient Corporation 2014 Omnibus Incentive Plan and previously reported on February 3, 2016.  Each PSU represents the right to receive one share of Navient Corporation (&quot;Navient&quot;) common stock in the future, which target amount vests at a specified percentage and is settled based upon achieving certain performance conditions over a three-year performance period ending on the final day of fiscal year 2018.  On January 30, 2019, the Compensation and Personnel Committee approved the achievement of the 2016 - 2018 PSUs at 125% of target resulting in the settling on February 28, 2019, of 23,828.75 shares of such PSUs and an additional 3,724.6326 shares were issued to the reporting person upon the vesting of the related dividend equivalent rights.  In connection with this settlement, 8,294 shares were withheld by Navient (as approved by the Navient Compensation and Personnel Committee) to satisfy the reporting person's tax withholding obligations.</footnote>
        <footnote id="F2">Reflects the disposition of 0.3826 shares settled in cash upon the delivery of the related dividend equivalent rights, in accordance with the terms of the 2014 Navient Corporation Omnibus Incentive Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Kurt T. Slawson (POA) for Stephen M. Hauber</signatureName>
        <signatureDate>2019-03-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
