Financing Receivable, Collateral Dependent

No definition available.

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Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118955202&loc=SL82895884-210446

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919249-210447

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919249-210447

+ Details

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

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

No definition available.

+ Details

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

- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5258-111524

+ Details

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

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

+ Details

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

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953550-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_MultifamilyMember
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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ewbc_ConstructionAndLandLoanMember
Namespace Prefix:
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- Details

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Data Type:	na
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- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_SingleFamilyMember
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- Details

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Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_CreditLossStatusAxis=ewbc_ReceivablesOriginatedOrAcquiredWithoutDeterioratedCreditQualityMember
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Data Type:	na
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- Details

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Loans Receivable and Allowance for Credit Losses (Impaired Loans) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018
Impaired loans disclosures
Allowance for loan losses	$ 317,894	$ 557,003		$ 358,287
Commercial and industrial (“C&I”)
Impaired loans disclosures
Allowance for loan losses		416
Commercial lending
Impaired loans disclosures
Collateral dependent loan		34,600
Commercial lending \| Commercial and industrial (“C&I”)
Impaired loans disclosures
Allowance for loan losses		362,629	$ 312,613	238,376
Commercial lending \| Commercial real estate (“CRE”)
Impaired loans disclosures
Allowance for loan losses		132,819	112,678	40,509
Commercial lending \| Real estate loan \| Multifamily residential
Impaired loans disclosures
Allowance for loan losses		16,530	14,714	22,826
Commercial lending \| Construction and land
Impaired loans disclosures
Allowance for loan losses		11,018	9,515	19,404
Consumer lending
Impaired loans disclosures
Collateral dependent loan		17,800
Consumer lending \| Real estate loan \| Single-family residential
Impaired loans disclosures
Allowance for loan losses		26,822	24,857	28,527
Consumer lending \| HELOCs
Impaired loans disclosures
Allowance for loan losses		3,881	3,467	5,265
Consumer lending \| Other consumer
Impaired loans disclosures
Allowance for loan losses		$ 3,304	$ 5,601	3,380
Non-PCI Loans
Impaired loans disclosures
Unpaid Principal Balance				266,772
Recorded Investment With No Allowance				129,748
Recorded Investment With Allowance				68,369
Total Recorded Investment				198,117
Related Allowance				5,593
Average Recorded Investment	159,152
Recognized Interest Income	1,056
Allowance for loan losses	317,880			358,287	$ 311,300
Non-PCI Loans \| Commercial lending
Impaired loans disclosures
Unpaid Principal Balance				226,918
Recorded Investment With No Allowance				115,116
Recorded Investment With Allowance				44,699
Total Recorded Investment				159,815
Related Allowance				3,033
Average Recorded Investment	129,939
Recognized Interest Income	910
Non-PCI Loans \| Commercial lending \| Commercial and industrial (“C&I”)
Impaired loans disclosures
Unpaid Principal Balance				174,656
Recorded Investment With No Allowance				73,956
Recorded Investment With Allowance				40,086
Total Recorded Investment				114,042
Related Allowance				2,881
Average Recorded Investment	93,391
Recognized Interest Income	735
Non-PCI Loans \| Commercial lending \| Commercial real estate (“CRE”)
Impaired loans disclosures
Unpaid Principal Balance				27,601
Recorded Investment With No Allowance				20,098
Recorded Investment With Allowance				1,520
Total Recorded Investment				21,618
Related Allowance				97
Average Recorded Investment	30,827
Recognized Interest Income	114
Non-PCI Loans \| Commercial lending \| Real estate loan \| Multifamily residential
Impaired loans disclosures
Unpaid Principal Balance				4,965
Recorded Investment With No Allowance				1,371
Recorded Investment With Allowance				3,093
Total Recorded Investment				4,464
Related Allowance				55
Average Recorded Investment	5,721
Recognized Interest Income	61
Non-PCI Loans \| Commercial lending \| Construction and land
Impaired loans disclosures
Unpaid Principal Balance				19,696
Recorded Investment With No Allowance				19,691
Recorded Investment With Allowance				0
Total Recorded Investment				19,691
Related Allowance				0
Non-PCI Loans \| Commercial lending \| Total CRE
Impaired loans disclosures
Unpaid Principal Balance				52,262
Recorded Investment With No Allowance				41,160
Recorded Investment With Allowance				4,613
Total Recorded Investment				45,773
Related Allowance				152
Average Recorded Investment	36,548
Recognized Interest Income	175
Non-PCI Loans \| Consumer lending
Impaired loans disclosures
Unpaid Principal Balance				39,854
Recorded Investment With No Allowance				14,632
Recorded Investment With Allowance				23,670
Total Recorded Investment				38,302
Related Allowance				2,560
Average Recorded Investment	29,213
Recognized Interest Income	146
Non-PCI Loans \| Consumer lending \| Real estate loan \| Single-family residential
Impaired loans disclosures
Unpaid Principal Balance				23,626
Recorded Investment With No Allowance				8,507
Recorded Investment With Allowance				13,704
Total Recorded Investment				22,211
Related Allowance				35
Average Recorded Investment	15,898
Recognized Interest Income	128
Non-PCI Loans \| Consumer lending \| HELOCs
Impaired loans disclosures
Unpaid Principal Balance				13,711
Recorded Investment With No Allowance				6,125
Recorded Investment With Allowance				7,449
Total Recorded Investment				13,574
Related Allowance				8
Average Recorded Investment	10,811
Recognized Interest Income	18
Non-PCI Loans \| Consumer lending \| Total residential mortgage
Impaired loans disclosures
Unpaid Principal Balance				37,337
Recorded Investment With No Allowance				14,632
Recorded Investment With Allowance				21,153
Total Recorded Investment				35,785
Related Allowance				43
Average Recorded Investment	26,709
Recognized Interest Income	146
Non-PCI Loans \| Consumer lending \| Other consumer
Impaired loans disclosures
Unpaid Principal Balance				2,517
Recorded Investment With No Allowance				0
Recorded Investment With Allowance				2,517
Total Recorded Investment				2,517
Related Allowance				$ 2,517
Average Recorded Investment	2,504
Recognized Interest Income	$ 0