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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-03-03</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001235820</rptOwnerCik>
            <rptOwnerName>DEGIORGIO KENNETH D</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>
            <isOfficer>1</isOfficer>
            <officerTitle>Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6095</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>52.95</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>390721</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4329</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>51.02</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>386392</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>128.078</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By 401(k) Plan Trust</value>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Payment of tax liability by withholding securities incident to the distribution of vested restricted stock units, which distribution was previously deferred.</footnote>
        <footnote id="F2">Includes 11,451 unvested Restricted Stock Units (&quot;RSUs&quot;) acquired pursuant to an original grant of 41,519 RSUs and shares acquired through automatic dividend reinvestment, vesting in four equal annual increments commencing 2/21/2019, the first anniversary of the grant.</footnote>
        <footnote id="F3">Includes 24,698 unvested RSUs acquired pursuant to an original grant of 46,231 RSUs and shares acquired through automatic dividend reinvestment, vesting in four equal annual increments commencing 2/22/2020, the first anniversary of the grant.</footnote>
        <footnote id="F4">Includes 35,320 unvested RSUs acquired pursuant to an original grant of 45,440 RSUs and shares acquired through automatic dividend reinvestment, vesting in four equal annual increments commencing 2/20/2021, the first anniversary of the grant.</footnote>
        <footnote id="F5">Includes 48,651 unvested RSUs acquired pursuant to a grant vesting in four equal annual increments commencing 2/18/2022, the first anniversary of the grant.</footnote>
        <footnote id="F6">The reporting person's receipt of certain shares underlying vested RSUs associated with various grants and related shares acquired through automatic dividend reinvestment have been deferred.</footnote>
        <footnote id="F7">Amount shown consists of shares contributed by issuer as company match, shares purchased for the reporting person's account and shares acquired through automatic reinvestment of dividends paid as reported in most recent account statement in transactions exempt under rules 16a-3(f)(1)(i)(B) and 16b-3(c).</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Greg L. Smith, Attorney-in-Fact for Kenneth D. DeGiorgio</signatureName>
        <signatureDate>2021-03-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
