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      <ContainEmbeddedReports>false</ContainEmbeddedReports>
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      <LongName>009084 - Disclosure - NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Impaired Non-covered Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/NonCoveredLoansAndAllowanceForLoanLossesImpairedNonCoveredLoansDetails</Role>
      <ShortName>NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Impaired Non-covered Loans) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>009085 - Disclosure - NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Allowance for Loan Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/NonCoveredLoansAndAllowanceForLoanLossesAllowanceForLoanLossesDetails</Role>
      <ShortName>NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Allowance for Loan Losses) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>009086 - Disclosure - NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Impairment Methodology) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/NonCoveredLoansAndAllowanceForLoanLossesImpairmentMethodologyDetails</Role>
      <ShortName>NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Impairment Methodology) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>009087 - Disclosure - NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Off-Balance Sheet) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/NonCoveredLoansAndAllowanceForLoanLossesOffBalanceSheetDetails</Role>
      <ShortName>NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Off-Balance Sheet) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>009090 - Disclosure - PREMISES AND EQUIPMENT (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/PremisesAndEquipmentDetails</Role>
      <ShortName>PREMISES AND EQUIPMENT (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>009100 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/GoodwillAndOtherIntangibleAssetsDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>009110 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>009120 - Disclosure - STOCKHOLDERS' EQUITY (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/StockholdersEquityDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>009121 - Disclosure - STOCKHOLDERS' EQUITY, Earnings (Loss) Per Share Calculations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/StockholdersEquityEarningsLossPerShareCalculationsDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY, Earnings (Loss) Per Share Calculations (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>009122 - Disclosure - STOCKHOLDERS' EQUITY, Shares Excluded From Calculation Of Diluted EPS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/StockholdersEquitySharesExcludedFromCalculationOfDilutedEpsDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY, Shares Excluded From Calculation Of Diluted EPS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>009130 - Disclosure - BUSINESS SEGMENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/BusinessSegmentsDetails</Role>
      <ShortName>BUSINESS SEGMENTS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>009140 - Disclosure - SUBSEQUENT EVENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://eastwestbank.com/role/SubsequentEventsDetails</Role>
      <ShortName>SUBSEQUENT EVENTS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <ContainEmbeddedReports>false</ContainEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
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  <Logs>
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    <Log type="Info">Element ewbc_AllowanceForNoncoveredLoansReceivable had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element ewbc_NoncoveredOtherRealEstateOwnedFairValueDisclosure had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element ewbc_CoveredOtherRealEstateOwnedFairValueDisclosure had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element ewbc_NoncoveredOtherRealEstateOwnedFairValueDisclosure had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element ewbc_CoveredOtherRealEstateOwnedFairValueDisclosure had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue had a mix of decimals attribute values: 2 0.</Log>
    <Log type="Info">Element us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue had a mix of decimals attribute values: 2 0.</Log>
    <Log type="Info">Element ewbc_VtotalAllowanceAllocatedToAdditionalAdvances had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element ewbc_AllowanceForNoncoveredLoansReceivable had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element us-gaap_FinancingReceivableModificationsRecordedInvestment had a mix of decimals attribute values: -5 -6.</Log>
    <Log type="Info">Element ewbc_AllowanceForNoncoveredLoansReceivable had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">Element us-gaap_FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability had a mix of decimals attribute values: -5 -7.</Log>
    <Log type="Info">Element us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion had a mix of decimals attribute values: 5 4.</Log>
    <Log type="Info">Element us-gaap_PreferredStockValue had a mix of decimals attribute values: -3 -5.</Log>
    <Log type="Info">'Monetary' elements on report '009030 - Disclosure - FAIR VALUE (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009033 - Disclosure - FAIR VALUE, Valuation Methodologies (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009040 - Disclosure - STOCK-BASED COMPENSATION (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009051 - Disclosure - INVESTMENT SECURITIES, Available-For-Sale Portfolio (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009054 - Disclosure - INVESTMENT SECURITIES, Unrealized Losses and Corporate Debt Securities (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009062 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS, Narrative (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009071 - Disclosure - COVERED ASSETS AND FDIC INDEMNIFICATION ASSET, Covered Assets and Credit Quality Indicators (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009072 - Disclosure - COVERED ASSETS AND FDIC INDEMNIFICATION ASSET, FDIC Indemnification Asset and FDIC Receivable (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009080 - Disclosure - NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009081 - Disclosure - NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES, Credit Quality Indicator (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009083 - Disclosure - NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Troubled Debt Restructurings) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009087 - Disclosure - NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Off-Balance Sheet) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009090 - Disclosure - PREMISES AND EQUIPMENT (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009100 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '009120 - Disclosure - STOCKHOLDERS' EQUITY (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 001000 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited)</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Jun. 30, 2011'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Sep. 30, 2010'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Jun. 30, 2010'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2009'</Log>
    <Log type="Info">Process Flow-Through: 001010 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 002000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited)</Log>
    <Log type="Info">	Process Flow-Through: Removing column '12 Months Ended
Dec. 31, 2010'</Log>
    <Log type="Info">Process Flow-Through: 003010 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY AND COMPREHENSIVE INCOME (Unaudited) (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 004000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)</Log>
    <Log type="Info">	Process Flow-Through: Removing column '12 Months Ended
Dec. 31, 2010'</Log>
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