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BASIS OF PRESENTATION (Details) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2014 trust | Sep. 30, 2014 trust
BASIS OF PRESENTATION |  |
Number of wholly owned subsidiaries that are statutory business trusts ("the Trusts") |  | 6
Number of acquisitions | 1 |

X
- Definition Represents the number of wholly owned subsidiaries of the entity that are statutory business trusts, which are not consolidated. + References No definition available. + Details
Name: | ewbc_NumberOfWhollyOwnedStatutoryBusinessTrusts
Namespace Prefix: | ewbc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of businesses acquired by the entity during the period. + References No definition available. + Details
Name: | us-gaap_NumberOfBusinessesAcquired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration