Loans Receivable and Allowance for Credit Losses - Allowance for Credit Losses Narrative (Details) $ in Millions	9 Months Ended
Sep. 30, 2022 USD ($) qtr	Dec. 31, 2021 USD ($)
Financing Receivable Allowance for Credit Losses
Life time loss rate, period span \| qtr	11
Allowance for credit losses	$ 606.6	$ 569.1
Increase in allowance for credit losses	$ 37.5
US Treasury Spread
Financing Receivable Allowance for Credit Losses
Credit derivative, term	10 years

Financing Receivable And Off Balance Sheet Credit Loss Allowance

No definition available.

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Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Financing Receivable And Off Balance Sheet Credit Loss Allowance, Period Increase (Decrease)

+ References

No definition available.

+ Details

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Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Life Time Loss Rate, Period Span

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of the credit risk derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5708775-113959

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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