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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-03-02</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001109264</rptOwnerCik>
            <rptOwnerName>REMONDI JOHN F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>123 S. JUSTISON STREET</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>WILMINGTON</rptOwnerCity>
            <rptOwnerState>DE</rptOwnerState>
            <rptOwnerZipCode>19801</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <officerTitle>Chief Executive Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>68001</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>12.89</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3075745.0459</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>250</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>As custodian for child</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents performance stock units (&quot;PSUs&quot;) awarded to the reporting person under the Navient Corporation 2014 Omnibus Incentive Plan and previously reported on February 5, 2018. 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 2020. On January 29, 2021, the Compensation and Personnel Committee approved the achievement of the 2018 - 2020 PSUs at 83% of target resulting in the settling on March 2, 2021, of 121,790.0500 shares of such PSUs and an additional 24,763.4015 shares were issued to the reporting person upon the vesting of the related dividend equivalent rights. In connection with this settlement, 68,001 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 0.4515 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>
        <footnote id="F3">The reporting person's common stock balance reflects the forfeiture of 30,016.9720 PSUs from the reporting person's beneficial ownership because the Company failed to meet the threshold performance level established for the PSUs granted for the 2018 - 2020 performance period.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Kurt T. Slawson (POA) for John F. Remondi</signatureName>
        <signatureDate>2021-03-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
