Loans Receivable and Allowance for Credit Losses - Schedule of Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Allowance for loan losses
ALLL, beginning of period	$ 809,773	$ 702,052	$ 702,052
Provision for (reversal of) credit losses on loans	37,874	48,062
Gross charge-offs	(20,779)	(16,983)
Gross recoveries	8,660	1,702
Total net (charge-offs) recoveries	(12,119)	(15,281)
Foreign currency translation adjustments	346	23
ALLL, end of period	835,874	734,856	809,773
Commercial Lending \| C&I
Allowance for loan losses
ALLL, beginning of period	475,613	384,319	384,319
Provision for (reversal of) credit losses on loans	17,892	36,370
Gross charge-offs	(18,385)	(988)
Gross recoveries	7,918	1,564
Total net (charge-offs) recoveries	(10,467)	576
Foreign currency translation adjustments	346	23
ALLL, end of period	483,384	421,288	475,613
Commercial Lending \| CRE
Allowance for loan losses
ALLL, beginning of period	221,494	218,677	218,677
Provision for (reversal of) credit losses on loans	11,160	8,105
Gross charge-offs	(1,305)	(13,937)
Gross recoveries	453	54
Total net (charge-offs) recoveries	(852)	(13,883)
Foreign currency translation adjustments	0	0
ALLL, end of period	231,802	212,899	221,494
Commercial Lending \| Multifamily Residential
Allowance for loan losses
ALLL, beginning of period	36,555	32,117	32,117
Provision for (reversal of) credit losses on loans	2,880	201
Gross charge-offs	0	(4)
Gross recoveries	11	10
Total net (charge-offs) recoveries	11	6
Foreign currency translation adjustments	0	0
ALLL, end of period	39,446	32,324	36,555
Commercial Lending \| Construction and land
Allowance for loan losses
ALLL, beginning of period	15,468	17,497	17,497
Provision for (reversal of) credit losses on loans	2,593	(305)
Gross charge-offs	(893)	(1,996)
Gross recoveries	2	3
Total net (charge-offs) recoveries	(891)	(1,993)
Foreign currency translation adjustments	0	0
ALLL, end of period	17,170	15,199	15,468
Consumer Lending \| SFR
Allowance for loan losses
ALLL, beginning of period	53,463	44,816	44,816
Provision for (reversal of) credit losses on loans	3,519	2,072
Gross charge-offs	(121)	(9)
Gross recoveries	22	50
Total net (charge-offs) recoveries	(99)	41
Foreign currency translation adjustments	0	0
ALLL, end of period	56,883	46,929	53,463
Consumer Lending \| HELOCs
Allowance for loan losses
ALLL, beginning of period	5,804	3,132	3,132
Provision for (reversal of) credit losses on loans	92	1,739
Gross charge-offs	0	0
Gross recoveries	3	8
Total net (charge-offs) recoveries	3	8
Foreign currency translation adjustments	0	0
ALLL, end of period	5,899	4,879	5,804
Consumer Lending \| Other Consumer
Allowance for loan losses
ALLL, beginning of period	1,376	1,494	1,494
Provision for (reversal of) credit losses on loans	(262)	(120)
Gross charge-offs	(75)	(49)
Gross recoveries	251	13
Total net (charge-offs) recoveries	176	(36)
Foreign currency translation adjustments	0	0
ALLL, end of period	$ 1,290	$ 1,338	$ 1,376

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of foreign currency translation gain (loss) which decreases (increases) allowance for credit loss on financing receivable. Excludes net investment in lease.

+ 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

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossForeignCurrencyTranslation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, excluding accrued interest, of decrease (increase) in allowance for credit loss on financing receivable from writeoff (recovery). Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476148/220-40-50-22

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ewbc_CommercialAndIndustrialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=srt_MultifamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ewbc_ConstructionAndLandLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=srt_SingleFamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ewbc_OtherConsumerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: