<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-05-16</periodOfReport>
    <issuer>
        <issuerCik>0000813461</issuerCik>
        <issuerName>WESTCORP /CA/</issuerName>
        <issuerTradingSymbol>wes</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0000885118</rptOwnerCik>
            <rptOwnerName>AMERICAN ASSETS INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>1</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock</value><footnoteId id="F1"/><footnoteId id="F2"/><footnoteId id="F3"/><footnoteId id="F4"/></securityTitle><transactionDate><value>2003-05-15</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>P</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>800</value></transactionShares><transactionValue><value>22.71</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>18239468</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value><footnoteId id="F1"/><footnoteId id="F2"/><footnoteId id="F3"/><footnoteId id="F4"/></securityTitle><transactionDate><value>2003-05-15</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>P</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>23700</value></transactionShares><transactionValue><value>22.75</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>18263668</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value><footnoteId id="F1"/><footnoteId id="F2"/><footnoteId id="F3"/><footnoteId id="F4"/></securityTitle><transactionDate><value>2003-05-15</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>P</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>500</value></transactionShares><transactionValue><value>22.73</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>18239968</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnotes><footnote id="F1">This filing is for the cumulative share holdings of an affiliated group as of July 31, 2002.  The various entities named in this report are owned directly and indirectly through a series of affiliated companies which are owned or controlled by Ernest S. Rady (Chairman of the Board of Westcorp).  The collective ownership of 26,940,377 shares of Common Stock of the issuer, represents 68.71% of the 39,206,084 outstanding shares of Common Stock of the issuer.  Schedule A attached hereto and incorporated by this reference herein depicts the relationship among the various affiliated companies in the &amp;quot;Rady group&amp;quot;.  There is no formal agreement to vote or dispose of the shares of the Issuer in a particular manner.  The dispositive and voting power of each of the individuals and companies shown on Schedule B is made independent of the other, except to the extent that Mr. and Mrs. Rady may be shareholders, officers and/or directors of the various companies and are able to control disposition and</footnote><footnote id="F2">Reporting persons disclaim beneficial interest.</footnote><footnote id="F3">Additional Holdings - Ernest Rady Trust - 4,064,750 / Evelyn Shirley Rady Trust - 273,432 / Explorer Insurance Co - 26,132 / Insurance Co of the West - 3,804,551 / DHM Trust - 437,162 / Ernest Rady 401k - 26,585 / Ernest Rady ESOP - 44,097</footnote><footnote id="F4">This is being amended to reflect change in amount of securities beneficially owned at end of month</footnote></footnotes><ownerSignature><signatureName>Guy Du Bose</signatureName><signatureDate>2003-06-12</signatureDate></ownerSignature></ownershipDocument>

