Securities - Continuous Unrealized Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	$ 2,510,007	$ 5,932,965
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(266,455)	(106,229)
Available-for-sale debt securities, 12 Months or More, Fair Value	3,258,297	1,778,987
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(599,568)	(66,622)
Available-for-sale debt securities fair value, Total	5,768,304	7,711,952
Available-for-sale debt securities, Gross Unrealized Loss, Total	(866,023)	(172,851)
U.S. Treasury securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	263,772	935,776
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(25,232)	(14,689)
Available-for-sale debt securities, 12 Months or More, Fair Value	336,905	47,881
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(50,403)	(1,998)
Available-for-sale debt securities fair value, Total	600,677	983,657
Available-for-sale debt securities, Gross Unrealized Loss, Total	(75,635)	(16,687)
U.S. government agency and U.S. government-sponsored enterprise debt securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	88,168	773,647
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(16,401)	(18,000)
Available-for-sale debt securities, 12 Months or More, Fair Value	172,256	402,907
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(42,245)	(16,710)
Available-for-sale debt securities fair value, Total	260,424	1,176,554
Available-for-sale debt securities, Gross Unrealized Loss, Total	(58,646)	(34,710)
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	334,460	440,734
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(39,330)	(13,589)
Available-for-sale debt securities, 12 Months or More, Fair Value	187,425	257,745
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(34,127)	(15,265)
Available-for-sale debt securities fair value, Total	521,885	698,479
Available-for-sale debt securities, Gross Unrealized Loss, Total	(73,457)	(28,854)
U.S. government agency and U.S. government-sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	700,318	2,138,542
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(72,088)	(37,691)
Available-for-sale debt securities, 12 Months or More, Fair Value	1,085,253	330,522
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(178,332)	(11,444)
Available-for-sale debt securities fair value, Total	1,785,571	2,469,064
Available-for-sale debt securities, Gross Unrealized Loss, Total	(250,420)	(49,135)
Municipal securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	203,157	177,065
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(46,271)	(5,682)
Available-for-sale debt securities, 12 Months or More, Fair Value	46,345	17,003
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(11,311)	(606)
Available-for-sale debt securities fair value, Total	249,502	194,068
Available-for-sale debt securities, Gross Unrealized Loss, Total	(57,582)	(6,288)
Non-agency commercial mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	170,101	301,925
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(8,351)	(4,158)
Available-for-sale debt securities, 12 Months or More, Fair Value	218,124	40,013
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(42,637)	(1,319)
Available-for-sale debt securities fair value, Total	388,225	341,938
Available-for-sale debt securities, Gross Unrealized Loss, Total	(50,988)	(5,477)
Non-agency residential mortgage-backed securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	188,584	707,792
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(23,168)	(8,966)
Available-for-sale debt securities, 12 Months or More, Fair Value	482,954	6,431
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(89,994)	(11)
Available-for-sale debt securities fair value, Total	671,538	714,223
Available-for-sale debt securities, Gross Unrealized Loss, Total	(113,162)	(8,977)
Corporate debt securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	247,533	183,916
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(24,969)	(3,084)
Available-for-sale debt securities, 12 Months or More, Fair Value	282,032	251,494
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(118,968)	(13,505)
Available-for-sale debt securities fair value, Total	529,565	435,410
Available-for-sale debt securities, Gross Unrealized Loss, Total	(143,937)	(16,589)
Foreign government bonds
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	68,733	27,097
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(336)	(5)
Available-for-sale debt securities, 12 Months or More, Fair Value	36,899	133,279
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(13,102)	(3,476)
Available-for-sale debt securities fair value, Total	105,632	160,376
Available-for-sale debt securities, Gross Unrealized Loss, Total	(13,438)	(3,481)
Asset-backed securities
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	54,811	24,885
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(1,579)	(301)
Available-for-sale debt securities, 12 Months or More, Fair Value	10,059	0
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(344)	0
Available-for-sale debt securities fair value, Total	64,870	24,885
Available-for-sale debt securities, Gross Unrealized Loss, Total	(1,923)	(301)
Collateralized loan obligations (“CLOs”)
Schedule of Available-for-sale Debt Securities
Available-for-sale debt securities, Less than 12 Months, Fair Value	190,370	221,586
Available-for-sale debt securities, Gross Unrealized Loss, Less than 12 Months	(8,730)	(64)
Available-for-sale debt securities, 12 Months or More, Fair Value	400,045	291,712
Available-for-sale debt securities, Gross Unrealized Loss, 12 Months or More	(18,105)	(2,288)
Available-for-sale debt securities fair value, Total	590,415	513,298
Available-for-sale debt securities, Gross Unrealized Loss, Total	$ (26,835)	$ (2,352)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922888-210455

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456

+ Details

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

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=ewbc_CommercialMortgageBackedSecuritiesIssuedByUSGovernmentAgenciesAndGovernmentSponsoredEnterpriseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=ewbc_ResidentialMortgageBackedSecuritiesIssuedByUSGovernmentAgenciesAndGovernmentSponsoredEnterpriseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=ewbc_ForeignGovernmentBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedLoanObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: