Name:	ewbc_AccruedInterestPayableFairValueDisclosure
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

No definition available.

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

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. The element may be used in both the balance sheet and disclosure. This item represents the aggregate of certain deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing, specifically demand deposits, saving deposits, and money market deposits.

No definition available.

Name:	ewbc_DemandSavingsAndMoneyMarketDepositsFairValueDisclosure
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the portion of the balance sheet assertion valued at fair value and may be used in connection with the fair value disclosures required in the footnotes. Federal Reserve Bank stock represents an equity interest in the Federal Reserve Bank.

No definition available.

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

Represents the portion of the balance sheet assertion valued at fair value and may be used in connection with the fair value disclosures required in the footnotes. This is the carrying value of funds outstanding loaned in the form of security resale agreements if the agreement requires the purchaser to resell the identical security purchased or a security meeting the definition of 'substantially the same.' Includes purchases of participations in pools of securities that are subject to a resale agreement.

No definition available.

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

No definition available.

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

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. The element may be used in both the balance sheet and disclosure. This item represents the aggregate of certain deposit liabilities held by the entity, including foreign and domestic, interest bearing, specifically time deposits.

No definition available.

Name:	ewbc_TimeDepositsFairValueDisclosure
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

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

Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13(3)(a))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

- Details

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

- Details

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

Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=29638263&loc=d3e39828-111592

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

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

No definition available.

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

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Glossary Loan

-URI http://asc.fasb.org/extlink&oid=6517073

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

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

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

Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13433-108611