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v3.19.3.a.u2

Summary of Significant Accounting Policies (Nature of Operations and Principles of Consolidation) (Details) | Dec. 31, 2019 location trust
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Accounting Policies [Abstract] |
Number of banking locations (more than) | location | 125
Principles of Consolidation |
Number of wholly owned subsidiaries that are statutory business trusts | trust | 6

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- Definition Represents the number of banking locations in which the entity operates. + References No definition available. + Details
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Namespace Prefix: | ewbc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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

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- References No definition available. + Details
Name: | ewbc_PrinciplesOfConsolidationAbstract
Namespace Prefix: | ewbc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration