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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-07-31</periodOfReport>

    <issuer>
        <issuerCik>0001136893</issuerCik>
        <issuerName>Fidelity National Information Services, Inc.</issuerName>
        <issuerTradingSymbol>FIS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001209456</rptOwnerCik>
            <rptOwnerName>PARENT LOUISE M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>601 RIVERSIDE AVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>JACKSONVILLE</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>32204</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-07-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>9</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1529</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the Agreement and Plan of Merger (the &quot;Merger Agreement&quot;), dated March 17, 2019, among Fidelity National Information Services, Inc. (&quot;FIS&quot;), Worldpay, Inc. (&quot;Worldpay&quot;), and Wrangler Merger Sub, Inc. (&quot;Merger Sub&quot;), a wholly-owned subsidiary of FIS, on July 31, 2019 (the &quot;Closing Date&quot;), Merger Sub merged with and into Worldpay (the &quot;Merger&quot;), with Worldpay continuing as the surviving corporation and a wholly-owned subsidiary of FIS. On the Closing Date, each share of Worldpay common stock held by the Reporting Person was converted into the right to receive 0.9287 shares of Issuer's common stock and $11.00 in cash. This form was not timely filed due to an inadvertent administrative error by Reporting Person's financial advisor, which delayed in advising Reporting Person that she had 10 shares of Worldpay stock in a managed account.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Marc M. Mayo, attorney-in-fact</signatureName>
        <signatureDate>2019-08-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
