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Basis of Presentation and Current Accounting Developments (Details) | Sep. 30, 2021 trust
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Accounting Policies [Abstract] |
Number of Wholly Owned Statutory Business Trusts | 6

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- 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
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Namespace Prefix: | ewbc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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