Name:	ewbc_AmountOfEligibleLossesOverWhichFdicIsObligatedToReimburseHigherPercentage
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Represents the change in the estimate of cash flows expected to be collected. This relates to a loan accounted for as an available-for-sale debt security, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

No definition available.

Name:	ewbc_ChangesInExpectedCashFlows
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

Name:	ewbc_FDICIndemnificationAssetLiabilitiesRollForward
Namespace Prefix:	ewbc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Increases (decreases) to the indemnification asset or liability due to accretion (amortization) of the loan discount (premium) relating to loss sharing agreements with the Federal Deposit Insurance Corporation (FDIC).

No definition available.

Name:	ewbc_FdicIndemnificationAccretionAmortizationOfDiscountPremium
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the carrying amount of receivable assets (liabilities) originating from the indemnification agreement with the Federal Deposit Insurance Corporation (FDIC), in which the FDIC is to partially cover losses.

No definition available.

Name:	ewbc_FdicIndemnificationAssetLiabilities
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Reductions (increases) in the FDIC indemnification asset (liability) resulting from write-offs, partial prepayments, loan payoffs and disposals.

No definition available.

Name:	ewbc_FdicIndemnificationAssetLiabilityReductionsIncreases
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Carrying amount of liabilities originating from the indemnification agreement with the Federal Deposit Insurance Corporation (FDIC), in which the FDIC is to partially cover losses.

No definition available.

Name:	ewbc_FdicIndemnificationLiability
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Change in the FDIC indemnification asset or liability for estimated amounts that the entity will be required to pay the FDIC at the end of the loss sharing agreements due to lower thresholds of losses.

No definition available.

Name:	ewbc_FdicRepayments
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Percentage obligation to reimburse the FDIC for eligible recoveries related to covered assets pursuant to the shared-loss agreements.

No definition available.

Name:	ewbc_PercentageObligationToReimburseFdicForEligibleRecoveriesRelatedToCoveredAssets
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage obligation to reimburse the FDIC for eligible recoveries related to losses in excess of a certain amount on covered assets pursuant to the shared-loss agreements.

No definition available.

Name:	ewbc_PercentageObligationToReimburseFdicForEligibleRecoveriesRelatedToLossesInExcessOfCertainAmountOnCoveredAssets
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of eligible losses for which the FDIC is obligated to reimburse the Company pursuant to the shared-loss agreements.

No definition available.

Name:	ewbc_PercentageOfEligibleLossesForWhichFdicIsObligatedToReimburse
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of eligible losses for covered assets in excess of a certain amount for which the FDIC is obligated to reimburse the Company pursuant to the shared-loss agreements.

No definition available.

Name:	ewbc_PercentageOfEligibleLossesInExcessOfCertainAmountForWhichFdicIsObligatedToReimburse
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 15

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=27045933&loc=d3e13503-111538

Name:	us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of decrease from accretion of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 15

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=27045933&loc=d3e13503-111538

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Name:	us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of additions to the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

Name:	us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

Name:	us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldMovementScheduleRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Aggregate gross carrying amount of loans and leases receivable covered by loss sharing agreements.

No definition available.

Name:	us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCovered
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_LoansReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FairValueByAssetClassAxis=ewbc_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_BusinessAcquisitionAxis=ewbc_UnitedCommercialBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ewbc_ReceivableByIndemnificationStatusAxis=ewbc_CoveredLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: