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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-01-08</periodOfReport>

    <notSubjectToSection16>false</notSubjectToSection16>

    <issuer>
        <issuerCik>0001096385</issuerCik>
        <issuerName>VECTREN CORP</issuerName>
        <issuerTradingSymbol>VVC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001194201</rptOwnerCik>
            <rptOwnerName>SMITH MICHAEL L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE VECTREN SQUARE</rptOwnerStreet1>
            <rptOwnerStreet2>P. O. BOX 209</rptOwnerStreet2>
            <rptOwnerCity>EVANSVILLE</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>47708</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.00</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2019-01-01</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2019-01-08</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>I</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1761.00</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>71.98</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1761.00</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16921.3883</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The reporting person received an optional scheduled distribution from the Vectren Corporation Nonqualified Deferred Compensation Plan pursuant to the terms of the Plan. The distribution elections were made during open enrollment for the 2012 Plan year.  This discretionary transaction is exempt under Rule 16b-3(b)(f).  Each share of phantom stock was the equivalent of one share of Vectren common stock.  Pursuant to the terms of the Plan, the phantom shares were payable in cash to the reporting person within 60 days of the scheduled distribution date.</footnote>
        <footnote id="F2">Phantom stock units held under the non-qualified deferred compensation plan will effectively be exercised at the time amounts represented by those units are paid out under the Plan. Generally, unless provided otherwise by the participant, the payout begins with the end of the board member's service as a member of the board. Pursuant to the non-qualified deferred compensation plan, payouts can occur for up to 15 years. Amounts held in the phantom stock accounts would be amortized over that period unless directed otherwise by the participant.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/Ronald E. Christian</signatureName>
        <signatureDate>2019-01-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
