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

The estimated liability that will be due to the FDIC forty-five days after the tenth anniversary of the acquisition of Washington First International Bank (WFIB) and United Commercial Bank (UCB). This liability is based on specific thresholds of losses no.

No definition available.

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

The number of days following the 10th anniversary of the respective acquisition date upon which the Company will be required to pay to the FDIC a calculated amount, based on the specific thresholds of losses not being reached.

No definition available.

Name:	ewbc_NumberOfDaysFollowingAnniversary
Namespace Prefix:	ewbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
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

The percentage of the asset discount, as defined in the shared-loss agreements, used in the calculation of this liability to the FDIC.

No definition available.

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

The percentage of the Cumulative Shared-Loss Payments, as defined in the shared-loss agreements, used in the calculation of this liability to the FDIC.

No definition available.

Name:	ewbc_PercentageOfCumulativeSharedLossPayments
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

The percentage of excess resulting from the calculation of this liability to the FDIC as stated in the shared-loss agreements.

No definition available.

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

The percentage of the Intrinsic Loss Estimate, as defined in the shared-loss agreements, used in the calculation of this liability to the FDIC.

No definition available.

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

Percentage of loans receivable acquired covered by shared-loss agreements with the FDIC.

No definition available.

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

- Details

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

Term of loan shared-loss agreement from the acquisition date.

No definition available.

Name:	ewbc_TermOflLoanSharedLossAgreement
Namespace Prefix:	ewbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Term of loss recovery provisions from the acquisition date for loans pursuant to the shared-loss agreements.

No definition available.