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

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

The carrying amount as of the balance sheet date of the FDIC loss sharing receivable which represents the amounts reimbursable from the FDIC that have not yet been received.

No definition available.

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

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

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

Represents the decrease in the FDIC indemnification asset due to estimated repayments.

No definition available.

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

The percentage of the actual expenses paid by the Company representing the net of the reimbursable expenses recorded in noninterest expense over the reimbursable expenses recorded in noninterest income.

No definition available.

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

The percentage of any reimbursable expense (chargeoffs, loan related expenses and OREO related expenses) that is recorded as noninterest income on the Condensed Consolidated Statement of Income.

No definition available.

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

Represents the percentage share of FDIC in recoveries received.

No definition available.

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

The percentage of reimbursable expenses (loan related and OREO expenses) recorded as non-interest expense on the Condensed Consolidated Statements of Income.

No definition available.

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

Reductions in the FDIC indemnification asset.

No definition available.

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

The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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

Amount of increases to the indemnification asset due to additional estimated losses assumed by the Federal Deposit Insurance Corporation (FDIC), relating to loss sharing agreements with the FDIC.

No definition available.

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

Amount of decreases to the indemnification asset due to cash payments received relating to loss sharing agreements with the Federal Deposit Insurance Corporation (FDIC).

No definition available.

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