Loans Receivable and Allowance for Credit Losses - Summary of Activities in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Allowance for loan losses
Allowance for loan losses, beginning of period	$ 545,685	$ 607,506	$ 541,579	$ 619,983
Provision for (reversal of) credit losses on loans	12,469	(8,790)	24,721	(7,739)
Gross charge-offs	(1,146)	(15,060)	(12,779)	(30,959)
Gross recoveries	7,730	1,785	11,099	4,278
Total net recoveries (charge-offs)	6,584	(13,275)	(1,680)	(26,681)
Foreign currency translation adjustment	(1,468)	283	(1,350)	161
Allowance for loan losses, end of period	563,270	585,724	563,270	585,724
Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Allowance for loan losses, beginning of period	339,446	394,084	338,252	398,040
Provision for (reversal of) credit losses on loans	19,030	(22,605)	28,292	(18,763)
Gross charge-offs	(240)	(10,572)	(11,428)	(19,008)
Gross recoveries	6,514	1,338	9,516	2,098
Total net recoveries (charge-offs)	6,274	(9,234)	(1,912)	(16,910)
Foreign currency translation adjustment	(1,468)	283	(1,350)	161
Allowance for loan losses, end of period	363,282	362,528	363,282	362,528
Commercial lending \| Commercial real estate (“CRE”)
Allowance for loan losses
Allowance for loan losses, beginning of period	147,104	146,399	150,940	163,791
Provision for (reversal of) credit losses on loans	(6,819)	19,375	(10,312)	9,098
Gross charge-offs	(671)	(4,134)	(1,069)	(11,329)
Gross recoveries	631	322	686	402
Total net recoveries (charge-offs)	(40)	(3,812)	(383)	(10,927)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	140,245	161,962	140,245	161,962
Commercial lending \| Residential loan \| Multifamily residential
Allowance for loan losses
Allowance for loan losses, beginning of period	24,176	27,407	14,400	27,573
Provision for (reversal of) credit losses on loans	1,976	(5,385)	11,633	(6,776)
Gross charge-offs	(8)	(113)	(9)	(130)
Gross recoveries	408	16	528	1,258
Total net recoveries (charge-offs)	400	(97)	519	1,128
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	26,552	21,925	26,552	21,925
Commercial lending \| Construction and land
Allowance for loan losses
Allowance for loan losses, beginning of period	11,016	19,089	15,468	10,239
Provision for (reversal of) credit losses on loans	(4,338)	(3,243)	(8,844)	5,349
Gross charge-offs	0	(209)	0	(280)
Gross recoveries	4	6	58	335
Total net recoveries (charge-offs)	4	(203)	58	55
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	6,682	15,643	6,682	15,643
Consumer lending \| Residential loan \| Single-family residential
Allowance for loan losses
Allowance for loan losses, beginning of period	18,210	15,839	17,160	15,520
Provision for (reversal of) credit losses on loans	3,461	609	4,387	985
Gross charge-offs	0	0	0	(134)
Gross recoveries	169	82	293	159
Total net recoveries (charge-offs)	169	82	293	25
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	21,840	16,530	21,840	16,530
Consumer lending \| HELOCs
Allowance for loan losses
Allowance for loan losses, beginning of period	3,748	2,670	3,435	2,690
Provision for (reversal of) credit losses on loans	(339)	250	(40)	272
Gross charge-offs	(193)	0	(193)	(45)
Gross recoveries	4	18	18	21
Total net recoveries (charge-offs)	(189)	18	(175)	(24)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	3,220	2,938	3,220	2,938
Consumer lending \| Other consumer
Allowance for loan losses
Allowance for loan losses, beginning of period	1,985	2,018	1,924	2,130
Provision for (reversal of) credit losses on loans	(502)	2,209	(395)	2,096
Gross charge-offs	(34)	(32)	(80)	(33)
Gross recoveries	0	3	0	5
Total net recoveries (charge-offs)	(34)	(29)	(80)	(28)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	$ 1,449	$ 4,198	$ 1,449	$ 4,198

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

No definition available.

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. Excludes net investment in lease.

+ 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 https://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 decreases (increases) allowance for credit loss on financing receivable. Excludes net investment in lease.

+ 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 https://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 https://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 https://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 https://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 https://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 https://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 https://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

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://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 https://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: