Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Allowance for loan losses
Allowance for loan losses, beginning of period	$ 541,579	$ 619,983
Gross charge-offs	(11,633)	(15,899)
Gross recoveries	3,369	2,493
Total net (charge-offs) recoveries	(8,264)	(13,406)
Foreign currency translation adjustment	118	(119)
Allowance for loan losses, end of period	545,685	607,506
Financing Receivable, Credit Loss, Expense (Reversal)	12,252	1,048
Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Allowance for loan losses, beginning of period	338,252	398,040
Gross charge-offs	(11,188)	(8,436)
Gross recoveries	3,002	760
Total net (charge-offs) recoveries	(8,186)	(7,676)
Foreign currency translation adjustment	118	(119)
Allowance for loan losses, end of period	339,446	394,084
Financing Receivable, Credit Loss, Expense (Reversal)	9,262	3,839
Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Allowance for loan losses, beginning of period	150,940	163,791
Gross charge-offs	(398)	(7,195)
Gross recoveries	55	80
Total net (charge-offs) recoveries	(343)	(7,115)
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	147,104	146,399
Financing Receivable, Credit Loss, Expense (Reversal)	(3,493)	(10,277)
Commercial lending \| Residential loan \| Multifamily residential
Allowance for loan losses
Allowance for loan losses, beginning of period	14,400	27,573
Gross charge-offs	(1)	(17)
Gross recoveries	120	1,242
Total net (charge-offs) recoveries	119	1,225
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	24,176	27,407
Financing Receivable, Credit Loss, Expense (Reversal)	9,657	(1,391)
Commercial lending \| Construction and land
Allowance for loan losses
Allowance for loan losses, beginning of period	15,468	10,239
Gross charge-offs	0	(71)
Gross recoveries	54	329
Total net (charge-offs) recoveries	54	258
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	11,016	19,089
Financing Receivable, Credit Loss, Expense (Reversal)	(4,506)	8,592
Consumer lending \| Residential loan \| Single-family residential
Allowance for loan losses
Allowance for loan losses, beginning of period	17,160	15,520
Gross charge-offs	0	(134)
Gross recoveries	124	77
Total net (charge-offs) recoveries	124	(57)
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	18,210	15,839
Financing Receivable, Credit Loss, Expense (Reversal)	926	376
Consumer lending \| HELOCs
Allowance for loan losses
Allowance for loan losses, beginning of period	3,435	2,690
Gross charge-offs	0	(45)
Gross recoveries	14	3
Total net (charge-offs) recoveries	14	(42)
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	3,748	2,670
Financing Receivable, Credit Loss, Expense (Reversal)	299	22
Consumer lending \| Other consumer
Allowance for loan losses
Allowance for loan losses, beginning of period	1,924	2,130
Gross charge-offs	(46)	(1)
Gross recoveries	0	2
Total net (charge-offs) recoveries	(46)	1
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	1,985	2,018
Financing Receivable, Credit Loss, Expense (Reversal)	$ 107	$ (113)

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

No definition available.

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

- Definition

Amount, after recoveries, of loans and leases that have been written-off.

+ References

No definition available.

+ Details

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

- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

+ 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 (increases) decreases allowance for credit loss on financing receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossForeignCurrencyTranslation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ 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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(11))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ 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: