Represents the maximum percentage of the top loss on the multifamily loans with limited recourse.

No definition available.

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

- Definition

The portion of the allowance for unfunded loan commitments, off-balance sheet credit exposures and recourse provisions specifically related to off-balance sheet loans sold and securitized.

+ References

No definition available.

+ Details

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

- Definition

This is the principal amount outstanding for sold or securitized loans only (across all types of loans).

+ References

No definition available.

+ Details

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

- Definition

Represents the principal amount outstanding of multifamily loans with limited recourse sold or securitized.

+ References

No definition available.

+ Details

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

- Definition

Represents the principal amount outstanding of single-family loans with full recourse sold or securitized.

+ References

No definition available.

+ Details

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

- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 6A

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=SL6742756-110258

+ Details

Name:	us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Details

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

- Definition

Amount of loss contingency liability.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

+ Details

Name:	us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

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

- Definition

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherCommitment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Details

Name:	dei_LegalEntityAxis=ewbc_EastWestBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationCaseAxis=ewbc_FAndFLLCAnd618InvestmentIncVEastWestBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=ewbc_LoansSecuritizedWithoutRecourseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=ewbc_LoansSoldWithoutRecourseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_GuaranteeObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

COMMITMENTS AND CONTINGENCIES (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 18, 2014
Other Commitments
Other Commitments	$ 114.7	$ 73.1
Loans Sold or Securitized with Recourse
Guarantees
Principal amount of single-family loans with full recourse sold or securitized	35.5	42.2
Principal amount of multifamily loans with limited recourse sold or securitized	214.3	296.6
Principal amount of loans sold or securitized	249.8	338.8
Recourse provision limitation, maximum percentage of the top loss on the multifamily loans	4.00%
Recourse reserve related to loan sales and securitizations totaled	2.2	3.2
Commitment to repurchase the loan	0
Loans Sold without Recourse
Guarantees
Principal amount of loans sold or securitized	781.4	818.2
Loans Securitized without Recourse
Guarantees
Principal amount of loans sold or securitized	162.8	193.8
F&F, LLC and 618 Investment, Inc. v. East West Bank
Litigation
Interim adjusted amount of the verdict			36.6
East West Bank \| F&F, LLC and 618 Investment, Inc. v. East West Bank
Litigation
Litigation accrual	$ 31.6