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

No definition available.

Name:	ewbc_PercentageLimitOfRecourseOnMultiFamilyLoans
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
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

Name:	ewbc_PrincipalAmountOutstandingOnLoansSoldOrSecuritized
Namespace Prefix:	ewbc_
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

- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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

- Details

Name:	us-gaap_GuaranteesAbstract
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

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=ewbc_LoansSoldOrSecuritizedWithFullRecourseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=ewbc_LoansSoldOrSecuritizedWithLimitedRecourseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=ewbc_LoansSoldOrSecuritizedWithRecourseMember
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:

COMMITMENTS AND CONTINGENCIES (Details 2) (USD $)	Mar. 31, 2015	Dec. 18, 2014	Dec. 31, 2014
F&F, LLC and 618 Investment, Inc. v. East West Bank \| East West Bank
Litigation
Interim adjusted amount of the verdict		$ 36,600,000
Litigation accrual	32,600,000
Loans Sold or Securitized with Recourse
Guarantees
Principal amount of loans sold or securitized	237,700,000		249,800,000
Recourse reserve	673,000		2,200,000
Loans Sold or Securitized with Full Recourse \| Residential \| Single-family
Guarantees
Principal amount of loans sold or securitized	34,300,000		35,500,000
Loans Sold or Securitized with Limited Recourse \| Residential \| Multifamily
Guarantees
Principal amount of loans sold or securitized	$ 203,400,000		$ 214,300,000
Recourse provision limitation, maximum percentage of the top loss on the multifamily loans	4.00%