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FEDERAL HOME LOAN BANK ADVANCES AND LONG-TERM DEBT (Details 4) (USD $) | 12 Months Ended | 0 Months Ended | 3 Months Ended
--- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Mar. 31, 2014 | Sep. 30, 2013
Capital Resources |  |  |  |  |
Minimum total consolidated assets for exclusion of trust preferred securities as Tier I regulatory capital | $ 15,000,000,000 ewbc_MinimumTotalConsolidatedAssetsForExclusionOfTrustPreferredSecuritiesAsTierIRegulatoryCapital |  |  |  |
Debt redeemed | 30,310,000 us-gaap_RepaymentsOfOtherLongTermDebt | 10,310,000 us-gaap_RepaymentsOfOtherLongTermDebt | 75,000,000 us-gaap_RepaymentsOfOtherLongTermDebt |  |
Long-term debt | 225,848,000 us-gaap_LongTermDebt | 226,868,000 us-gaap_LongTermDebt |  |  |
Junior Subordinated Debt |  |  |  |  |
Capital Resources |  |  |  |  |
Number of statutory business trusts formed for the purpose of issuing junior subordinated debt to third party investors | 6 ewbc_NumberOfStatutoryBusinessTrustsFormedForIssuingDebtToThirdPartyInvestors / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Number of junior subordinated debts called | 1 ewbc_NumberOfJuniorSubordinatedDebtsCalled / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Common stock issued by the Trusts to the Company | 4,600,000 us-gaap_CommonStockHeldInTrust / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember | 3,900,000 us-gaap_CommonStockHeldInTrust / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
Minimum total consolidated assets for exclusion of trust preferred securities as Tier I regulatory capital | 15,000,000,000 ewbc_MinimumTotalConsolidatedAssetsForExclusionOfTrustPreferredSecuritiesAsTierIRegulatoryCapital / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Debt instrument, phased out (as a percent) |  | 25.00%ewbc_DebtInstrumentPhasedOutPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
Debt instrument, phased out period |  | 4 years |  |  |
Stated Interest Rate, base | three-month LIBOR |  |  |  |
Balance at the end of the period | 148,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember | 123,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
Long-term debt | 145,848,000 us-gaap_LongTermDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember | 126,868,000 us-gaap_LongTermDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
Term loan |  |  |  |  |
Capital Resources |  |  |  |  |
Stated Interest Rate, base | three-month LIBOR |  |  |  |
Stated Interest Rate, basis spread (as a percent) | 1.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_LongtermDebtTypeAxis = us-gaap_LoansPayableMember |  |  |  |
Interest rate as of reporting date (as a percent) | 1.81%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_LoansPayableMember |  |  |  |
Issue of debt |  |  |  |  | 100,000,000 us-gaap_DebtInstrumentFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_LoansPayableMember
Maturity period of debt |  |  |  |  | 3 years
Quarterly installment |  |  |  | 5,000,000 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_LongtermDebtTypeAxis = us-gaap_LoansPayableMember |
Final, lump sum repayment at maturity of debt instrument | 50,000,000 ewbc_DebtInstrumentLumpSumFinalPaymentBalloonPaymentAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_LoansPayableMember |  |  |  |
Long-term debt | 80,000,000 us-gaap_LongTermDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_LoansPayableMember | 100,000,000 us-gaap_LongTermDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_LoansPayableMember |  |  |
East West Capital Trust IV | Junior Subordinated Debt |  |  |  |  |
Capital Resources |  |  |  |  |
Stated Interest Rate, base | 3-month Libor + |  |  |  |
Stated Interest Rate, basis spread (as a percent) | 2.55%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustIVMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Balance at the end of the period |  | 10,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustIVMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
Debt redeemed | 10,000,000 us-gaap_RepaymentsOfOtherLongTermDebt / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustIVMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Stock redeemed | 310,000 us-gaap_StockRedeemedOrCalledDuringPeriodValue / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustIVMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
East West Capital Trust V | Junior Subordinated Debt |  |  |  |  |
Capital Resources |  |  |  |  |
Stated Interest Rate, base | 3-month Libor + |  |  |  |
Stated Interest Rate, basis spread (as a percent) | 1.80%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Interest rate as of reporting date (as a percent) | 2.03%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Balance at the end of the period | 15,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember | 15,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
East West Capital Trust VI | Junior Subordinated Debt |  |  |  |  |
Capital Resources |  |  |  |  |
Stated Interest Rate, base | 3-month Libor + |  |  |  |
Stated Interest Rate, basis spread (as a percent) | 1.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Interest rate as of reporting date (as a percent) | 1.74%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Balance at the end of the period | 20,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember | 20,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
East West Capital Trust VII | Junior Subordinated Debt |  |  |  |  |
Capital Resources |  |  |  |  |
Stated Interest Rate, base | 3-month Libor + |  |  |  |
Stated Interest Rate, basis spread (as a percent) | 1.35%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Interest rate as of reporting date (as a percent) | 1.59%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Balance at the end of the period | 30,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember | 30,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
East West Capital Trust VIII | Junior Subordinated Debt |  |  |  |  |
Capital Resources |  |  |  |  |
Stated Interest Rate, base | 3-month Libor + |  |  |  |
Stated Interest Rate, basis spread (as a percent) | 1.40%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIIIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Interest rate as of reporting date (as a percent) | 1.64%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIIIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Balance at the end of the period | 18,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIIIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember | 18,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustVIIIMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
East West Capital Trust IX | Junior Subordinated Debt |  |  |  |  |
Capital Resources |  |  |  |  |
Stated Interest Rate, base | 3-month Libor + |  |  |  |
Stated Interest Rate, basis spread (as a percent) | 1.90%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustIXMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Interest rate as of reporting date (as a percent) | 2.14%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustIXMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Balance at the end of the period | 30,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustIXMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember | 30,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_EastWestCapitalTrustIXMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |
Metro Bank Trust | Junior Subordinated Debt |  |  |  |  |
Capital Resources |  |  |  |  |
Reduction of a purchase accounting adjustment | 6,800,000 us-gaap_GoodwillPurchaseAccountingAdjustments / us-gaap_DebtInstrumentAxis = ewbc_MetroBankTrustMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Common stock issued by the Trusts to the Company | 1,100,000 us-gaap_CommonStockHeldInTrust / us-gaap_DebtInstrumentAxis = ewbc_MetroBankTrustMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Stated Interest Rate, base | 3-month Libor + |  |  |  |
Stated Interest Rate, basis spread (as a percent) | 1.55%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_DebtInstrumentAxis = ewbc_MetroBankTrustMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Interest rate as of reporting date (as a percent) | 1.79%us-gaap_DebtInstrumentInterestRateEffectivePercentage / us-gaap_DebtInstrumentAxis = ewbc_MetroBankTrustMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |
Balance at the end of the period | $ 35,000,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_DebtInstrumentAxis = ewbc_MetroBankTrustMember / us-gaap_LongtermDebtTypeAxis = us-gaap_JuniorSubordinatedDebtMember |  |  |  |

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