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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-02-03</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 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>2017-02-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20171</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.49</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1304644.4384</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-02-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4915</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.49</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1299728.4544</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-02-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>30077</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.49</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1269650.9496</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-02-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>77519</value>
                    <footnoteId id="F6"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1347169.9496</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-02-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>129198</value>
                    <footnoteId id="F7"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1476367.9496</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>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>15.48</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-02-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>297397</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F8"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-02-06</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>297397</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>297397</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">As previously reported, on February 3, 2016, Mr. Remondi was granted 125,816 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 3, 2017, 41,938 shares of such RSUs were settled and an additional 2,033 shares were issued to Mr. Remondi upon the vesting of the related dividend equivalent rights.  In connection with this settlement, 20,171 shares were withheld by Navient (as approved by the Navient Compensation and Personnel Committee) to satisfy Mr. Remondi's tax withholding obligations.</footnote>
        <footnote id="F2">As previously reported, in connection with the April 30, 2014 separation of Navient from SLM Corporation (&quot;SLM&quot;), Navient established the Navient Corporation 2014 Omnibus Incentive Plan and issued new Navient equity awards to holders of outstanding SLM equity awards in order to maintain the intrinsic value of prior SLM award grants. On April 30, 2014, Mr. Remondi was granted 28,512 vested RSUs representing the right to receive shares of Navient common stock in the future, subject to transfer restrictions which lapse in one-third increments on February 4, 2015, February 4, 2016 and February 4, 2017. On February 4, 2017, 9,504 shares of such RSUs were settled and an additional 1,200.9840 shares were issued to Mr. Remondi upon the delivery of the related dividend equivalent rights.  In connection with this settlement, 4,915 shares were withheld by Navient (as approved by the Navient Compensation and Personnel Committee) to satisfy Mr. Remondi's tax withholding obligations.</footnote>
        <footnote id="F3">Also reflects the disposition of 0.9840 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="F4">As previously reported, in connection with the April 30, 2014 separation of Navient from SLM, Navient established the Navient Corporation 2014 Omnibus Incentive Plan and issued new Navient equity awards to holders of outstanding SLM equity awards in order to maintain the intrinsic value of prior SLM award grants. On April 30, 2014, Mr. Remondi was granted 166,041 RSUs representing the right to receive shares of Navient common stock in the future, which vest in one-third increments on February 4, 2015, February 4, 2016 and February 4, 2017. On February 4, 2017, 55,347 shares of such RSUs were settled and an additional 6,987.5048 shares were issued to Mr. Remondi upon the vesting of the related dividend equivalent rights.  In connection with this settlement, 30,077 shares were withheld by Navient (as approved by the Navient Compensation and Personnel Committee) to satisfy Mr. Remondi's tax withholding obligations.</footnote>
        <footnote id="F5">Also reflects the disposition of 0.5048 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="F6">Grant of RSUs 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="F7">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 2019.  The performance conditions to be used shall be those approved by the Committee in connection with the Company's 2017 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="F8">Grant of net-settled stock options under the Navient Corporation 2014 Omnibus Incentive Plan. These options vest in one-third increments on each of the first, second and third anniversaries of the grant date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Kurt T. Slawson (POA) for John F. Remondi</signatureName>
        <signatureDate>2017-02-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
