Loans Receivable and Allowance for Credit Losses - Summary of Activities in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Allowance for loan losses
Allowance for loan losses, December 31, 2022			$ 595,645
Allowance for loan losses, December 31, 2022	$ 595,645	$ 541,579
Provision for (reversal of) credit losses on loans	18,520	12,252
Gross charge-offs	(2,037)	(11,633)
Gross recoveries	1,428	3,369
Total net (charge-offs) recoveries	(609)	(8,264)
Foreign currency translation adjustment	309	118
Allowance for loan losses, end of period	619,893	545,685
Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Allowance for loan losses, December 31, 2022			371,700
Allowance for loan losses, December 31, 2022		338,252
Provision for (reversal of) credit losses on loans	(678)	9,262
Gross charge-offs	(1,900)	(11,188)
Gross recoveries	1,211	3,002
Total net (charge-offs) recoveries	(689)	(8,186)
Foreign currency translation adjustment	309	118
Allowance for loan losses, end of period	376,325	339,446
Commercial lending \| CRE
Allowance for loan losses
Allowance for loan losses, December 31, 2022			149,864
Allowance for loan losses, December 31, 2022		150,940
Provision for (reversal of) credit losses on loans	4,676	(3,493)
Gross charge-offs	(6)	(398)
Gross recoveries	196	55
Total net (charge-offs) recoveries	190	(343)
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	155,067	147,104
Commercial lending \| Residential loan \| Multifamily residential
Allowance for loan losses
Allowance for loan losses, December 31, 2022			23,373
Allowance for loan losses, December 31, 2022		14,400
Provision for (reversal of) credit losses on loans	1,135	9,657
Gross charge-offs	0	(1)
Gross recoveries	12	120
Total net (charge-offs) recoveries	12	119
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	24,526	24,176
Commercial lending \| Construction and land
Allowance for loan losses
Allowance for loan losses, December 31, 2022			9,109
Allowance for loan losses, December 31, 2022		15,468
Provision for (reversal of) credit losses on loans	210	(4,506)
Gross charge-offs	0	0
Gross recoveries	3	54
Total net (charge-offs) recoveries	3	54
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	9,322	11,016
Consumer lending \| Residential loan \| Single-family residential
Allowance for loan losses
Allowance for loan losses, December 31, 2022			35,564
Allowance for loan losses, December 31, 2022		17,160
Provision for (reversal of) credit losses on loans	12,442	926
Gross charge-offs	0	0
Gross recoveries	0	124
Total net (charge-offs) recoveries	0	124
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	48,007	18,210
Consumer lending \| HELOCs
Allowance for loan losses
Allowance for loan losses, December 31, 2022			4,475
Allowance for loan losses, December 31, 2022		3,435
Provision for (reversal of) credit losses on loans	580	299
Gross charge-offs	(91)	0
Gross recoveries	6	14
Total net (charge-offs) recoveries	(85)	14
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	4,971	3,748
Consumer lending \| Other consumer
Allowance for loan losses
Allowance for loan losses, December 31, 2022			1,560
Allowance for loan losses, December 31, 2022		1,924
Provision for (reversal of) credit losses on loans	155	107
Gross charge-offs	(40)	(46)
Gross recoveries	0	0
Total net (charge-offs) recoveries	(40)	(46)
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	1,675	$ 1,985
Accounting Standards Update 2022-02
Allowance for loan losses
Impact of ASU 2022-02 adoption			6,028
Allowance for loan losses, December 31, 2022	$ (6,000)
Accounting Standards Update 2022-02 \| Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Impact of ASU 2022-02 adoption			5,683
Accounting Standards Update 2022-02 \| Commercial lending \| CRE
Allowance for loan losses
Impact of ASU 2022-02 adoption			337
Accounting Standards Update 2022-02 \| Commercial lending \| Residential loan \| Multifamily residential
Allowance for loan losses
Impact of ASU 2022-02 adoption			6
Accounting Standards Update 2022-02 \| Commercial lending \| Construction and land
Allowance for loan losses
Impact of ASU 2022-02 adoption			0
Accounting Standards Update 2022-02 \| Consumer lending \| Residential loan \| Single-family residential
Allowance for loan losses
Impact of ASU 2022-02 adoption			1
Accounting Standards Update 2022-02 \| Consumer lending \| HELOCs
Allowance for loan losses
Impact of ASU 2022-02 adoption			1
Accounting Standards Update 2022-02 \| Consumer lending \| Other consumer
Allowance for loan losses
Impact of ASU 2022-02 adoption			$ 0

Financing Receivable Allowance For Credit Loss Excluding Accrued Interest Before Impact of Adoption

No definition available.

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

- Definition

Financing Receivable Allowance For Credit Loss Excluding Accrued Interest Impact of Adoption

+ References

No definition available.

+ Details

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

- Definition

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

+ References

+ Details

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

- Definition

Amount, after recovery, of writeoff of financing receivable, charged against allowance for credit loss.

+ 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/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479294/326-20-55-79

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (4)
-Publisher SEC

+ Details

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

- Definition

Amount of increase in allowance for credit loss on financing receivable from recovery.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479294/326-20-55-79

Reference 2: 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

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 11B
-Subparagraph (c)(4)
-SubTopic 10
-Topic 310
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-11B

+ Details

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

- Definition

Amount of writeoff of financing receivable, charged against allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479294/326-20-55-79

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

Reference 3: 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 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-SubTopic 10
-Topic 310
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-11B

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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 of credit loss expense (reversal of expense) for financing receivable.

+ 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 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(11))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Name:	us-gaap_ProvisionForLoanLossesExpensed
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=us-gaap_RealEstateLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=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:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=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:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate202202Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: