Loans Receivable and Allowance for Credit Losses - Allowance for Credit Losses Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2023 USD ($) qtr	Dec. 31, 2022 USD ($)
Financing Receivable Allowance for Credit Losses
Life time loss rate, period span \| qtr	11
Allowance for credit losses	$ 647.6	$ 621.9
Increase in allowance for credit losses	$ 25.7
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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Balance Type:	credit
Period Type:	duration

- Definition

Life Time Loss Rate, Period Span

+ References

No definition available.

+ Details

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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
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (a)(1)
-SubTopic 10
-Topic 815
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4K

+ Details

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Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph c
-Publisher SEC

+ Details

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- Details

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