Name:	ewbc_DailyAverageReserveRequirement
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Regulatory Capital, Transition Capital Conservation Buffer

No definition available.

Name:	ewbc_RegulatoryCapitalTransitionCapitalConservationBuffer
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Regulatory Capital, Transition Capital Conservation Buffer, Phase In Period

No definition available.

Name:	ewbc_RegulatoryCapitalTransitionCapitalConservationBufferPhaseInPeriod
Namespace Prefix:	ewbc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Tier One Common Equity For Capital Adequacy To Risk Weighted Assets

No definition available.

Name:	ewbc_TierOneCommonEquityForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Name:	us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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.

No definition available.

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

The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826