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Summary of Significant Accounting Policies (Nature of Operations and Principles of Consolidation) (Details) | Dec. 31, 2017 location trust
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Accounting Policies [Abstract] |
Number of banking locations | location | 130
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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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
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Namespace Prefix: | ewbc_
Data Type: | xbrli:integerItemType
Balance Type: | na
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- References No definition available. + Details
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Namespace Prefix: | ewbc_
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Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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