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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-02-21</periodOfReport>

    <issuer>
        <issuerCik>0001472787</issuerCik>
        <issuerName>First American Financial Corp</issuerName>
        <issuerTradingSymbol>FAF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001202205</rptOwnerCik>
            <rptOwnerName>DOTI  JAMES L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1 FIRST AMERICAN WAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SANTA ANA</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92707</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-02-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1750</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>56107.614</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Includes 979 unvested Restricted Sock Units (&quot;RSUs&quot;) acquired pursuant to an original grant of 2,671 RSUs, and shares acquired through automatic dividend reinvestment, vesting in three equal annual increments commencing 2/25/16, the first anniversary of the grant.</footnote>
        <footnote id="F2">Includes 1,803 unvested RSUs acquired pursuant to an original grant of 2,541 RSUs, and shares acquired through automatic dividend reinvestment, vesting in three equal annual increments commencing 2/23/17, the first anniversary of the grant.</footnote>
        <footnote id="F3">Includes 2,191 unvested RSUs acquired pursuant to an original grant  of 3,174 RSUs, and shares acquired through automatic dividend reinvestment, vesting in three equal annual increments commencing 12/20/17, the first anniversary of the grant.</footnote>
        <footnote id="F4">Includes 1,592 unvested RSUs acquired pursuant to a grant vesting on 12/20/18.</footnote>
        <footnote id="F5">Includes 1,750 unvested RSUs acquired pursuant to a grant vesting 2/21/19.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Greg L. Smith, attorney-in-fact for James L. Doti</signatureName>
        <signatureDate>2018-02-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
