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FAIR VALUE MEASUREMENT AND FAIR VALUE OF FINANCIAL INSTRUMENTS (Details 3) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013
Quantitative information |  |  |  |
Investment securities available-for-sale | 2,626,365 us-gaap_AvailableForSaleSecurities |  | 2,733,797 us-gaap_AvailableForSaleSecurities |
Corporate debt securities | Non-investment grade |  |  |  |
Quantitative information |  |  |  |
Investment securities available-for-sale | 14,681 us-gaap_AvailableForSaleSecurities / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember | [1] | 15,101 us-gaap_AvailableForSaleSecurities / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember | [1]
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) |  |  |  |
Quantitative information |  |  |  |
Investment securities available-for-sale | 6,528 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 6,371 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |
Fair Value, Measurements, Recurring | Embedded Derivative Liabilities | Discounted cash flow | Significant Unobservable Inputs (Level 3) |  |  |  |
Quantitative information |  |  |  |
Derivative liabilities | (3,392)us-gaap_DerivativeLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByLiabilityClassAxis = us-gaap_EmbeddedDerivativeFinancialInstrumentsMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | (3,655)us-gaap_DerivativeLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByLiabilityClassAxis = us-gaap_EmbeddedDerivativeFinancialInstrumentsMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Fair Value, Measurements, Recurring | Embedded Derivative Liabilities | Discounted cash flow | Significant Unobservable Inputs (Level 3) | Minimum |  |  |  |
Quantitative information |  |  |  |
Credit risk | 0.115%ewbc_FairValueInputsCreditRiskAdjustmentRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByLiabilityClassAxis = us-gaap_EmbeddedDerivativeFinancialInstrumentsMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 0.175%ewbc_FairValueInputsCreditRiskAdjustmentRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByLiabilityClassAxis = us-gaap_EmbeddedDerivativeFinancialInstrumentsMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Fair Value, Measurements, Recurring | Embedded Derivative Liabilities | Discounted cash flow | Significant Unobservable Inputs (Level 3) | Maximum |  |  |  |
Quantitative information |  |  |  |
Credit risk | 0.142%ewbc_FairValueInputsCreditRiskAdjustmentRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByLiabilityClassAxis = us-gaap_EmbeddedDerivativeFinancialInstrumentsMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 0.212%ewbc_FairValueInputsCreditRiskAdjustmentRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByLiabilityClassAxis = us-gaap_EmbeddedDerivativeFinancialInstrumentsMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Fair Value, Measurements, Recurring | Embedded Derivative Liabilities | Discounted cash flow | Significant Unobservable Inputs (Level 3) | Weighted Average |  |  |  |
Quantitative information |  |  |  |
Credit risk | 0.133%ewbc_FairValueInputsCreditRiskAdjustmentRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByLiabilityClassAxis = us-gaap_EmbeddedDerivativeFinancialInstrumentsMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 0.20%ewbc_FairValueInputsCreditRiskAdjustmentRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByLiabilityClassAxis = us-gaap_EmbeddedDerivativeFinancialInstrumentsMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Fair Value, Measurements, Recurring | Corporate debt securities | Non-investment grade | Significant Unobservable Inputs (Level 3) |  |  |  |
Quantitative information |  |  |  |
Investment securities available-for-sale | 6,528 us-gaap_AvailableForSaleSecurities / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember |  | 6,371 us-gaap_AvailableForSaleSecurities / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember |
Fair Value, Measurements, Recurring | Corporate debt securities | Non-investment grade | Discounted cash flow | Significant Unobservable Inputs (Level 3) |  |  |  |
Quantitative information |  |  |  |
Investment securities available-for-sale | 6,528 us-gaap_AvailableForSaleSecurities / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 6,371 us-gaap_AvailableForSaleSecurities / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Loss severity | 85.00%us-gaap_FairValueInputsLossSeverity / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 85.00%us-gaap_FairValueInputsLossSeverity / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Fair Value, Measurements, Recurring | Corporate debt securities | Non-investment grade | Discounted cash flow | Significant Unobservable Inputs (Level 3) | Minimum |  |  |  |
Quantitative information |  |  |  |
Constant prepayment rate | 0.00%us-gaap_FairValueInputsPrepaymentRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 0.00%us-gaap_FairValueInputsPrepaymentRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Constant default rate | 0.75%us-gaap_FairValueInputsProbabilityOfDefault / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 0.75%us-gaap_FairValueInputsProbabilityOfDefault / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Discount margin | 4.50%us-gaap_FairValueInputsDiscountRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 6.50%us-gaap_FairValueInputsDiscountRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Fair Value, Measurements, Recurring | Corporate debt securities | Non-investment grade | Discounted cash flow | Significant Unobservable Inputs (Level 3) | Maximum |  |  |  |
Quantitative information |  |  |  |
Constant prepayment rate | 1.00%us-gaap_FairValueInputsPrepaymentRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 1.00%us-gaap_FairValueInputsPrepaymentRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Constant default rate | 1.20%us-gaap_FairValueInputsProbabilityOfDefault / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 1.20%us-gaap_FairValueInputsProbabilityOfDefault / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Discount margin | 7.50%us-gaap_FairValueInputsDiscountRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 11.50%us-gaap_FairValueInputsDiscountRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Fair Value, Measurements, Recurring | Corporate debt securities | Non-investment grade | Discounted cash flow | Significant Unobservable Inputs (Level 3) | Weighted Average |  |  |  |
Quantitative information |  |  |  |
Constant prepayment rate | 0.73%us-gaap_FairValueInputsPrepaymentRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 0.74%us-gaap_FairValueInputsPrepaymentRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Constant default rate | 0.87%us-gaap_FairValueInputsProbabilityOfDefault / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 0.87%us-gaap_FairValueInputsProbabilityOfDefault / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Loss severity | 85.00%us-gaap_FairValueInputsLossSeverity / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 85.00%us-gaap_FairValueInputsLossSeverity / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
Discount margin | 6.94%us-gaap_FairValueInputsDiscountRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |  | 9.97%us-gaap_FairValueInputsDiscountRate / us-gaap_ExternalCreditRatingByGroupingAxis = us-gaap_ExternalCreditRatingNonInvestmentGradeMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateDebtSecuritiesMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = ewbc_DiscountedCashFlowValuationTechniqueMember |
[1] | Investment securities rated BBB- or higher by S&P, or Baa3 or higher by Moody are considered investment grade. Conversely, investment securities rated below BBB- by S&P, or below Baa3 by Moody are considered non-investment grade.

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- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13495-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226008-175313 + Details
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