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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-02-05</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>2019-02-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>174825</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2141000.3473</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>262237</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2403237.3473</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8721</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.44</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2394516.3473</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>12040</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.42</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2382476.3473</value>
                </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">Grant of restricted stock units (&quot;RSUs&quot;) under the Navient Corporation 2014 Omnibus Incentive Plan, which is classified as &quot;Common Stock,&quot; as permitted, since the RSUs will be settled solely by delivery of shares of Navient common stock. These RSUs vest in one-third increments on each of the first, second and third anniversaries of the grant date.</footnote>
        <footnote id="F2">Grant of Performance Stock Units (&quot;PSUs&quot;) which is classified as &quot;Common Stock,&quot; as permitted, since the PSUs will be settled solely by delivery of shares of the Company's common stock upon vesting.  A specified percentage of this target award will vest and be settled based upon the satisfaction of certain performance conditions over a three-year performance period ending on the final day of fiscal year 2021.  The performance conditions to be used shall be those approved by the Committee in connection with the Company's 2019 Long-Term Incentive Program and shall be set forth in the form of PSU award agreement approved by the Committee.  Each vested PSU will be settled in shares of the Company's common stock.</footnote>
        <footnote id="F3">As previously reported, on February 5, 2018, the reporting person was granted 58,694 RSUs 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 5, 2019, 18,742 shares of such RSUs were settled and an additional 1,031 shares were issued to the reporting person upon the vesting of the related dividend equivalent rights.  In connection with this settlement, 8,721 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>
        <footnote id="F4">As previously reported, on February 6, 2017, the reporting person was granted 77,519 RSUs 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, 2019, 24,754 shares of such RSUs were settled and an additional 2,545 shares were issued to the reporting person upon the vesting of the related dividend equivalent rights.  In connection with this settlement, 12,040 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 John F. Remondi</signatureName>
        <signatureDate>2019-02-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
