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

The minimum number of quoted market prices obtained from independent external brokers that have traditionally been used in determining the fair values of level 3 available-for-sale securities.

No definition available.

Name:	ewbc_NumberOfQuotedMarketPricesTraditionallyUsedInDeterminingFairValueOfPrivateLabelMortgageBackedSecuritiesAndPooledTrustPreferredSecurities
Namespace Prefix:	ewbc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The maximum percentage of total available-for-sale securities represented by the Company's Level 3 available-for-sale securities.

No definition available.

Name:	ewbc_PercentageOfTotalAvailableForSaleSecuritiesRepresentedByLevel3AvailableForSaleSecurities
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The term of the contract (in years) associated with the derivative instrument.

No definition available.

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

The term of original maturity that securities purchased under resale agreements must exceed to be included in certain fair value calculations. The fair value of securities purchased under resale agreements exceeding this term of original maturity is estimated by discounting the cash flows based on expected maturities or re-pricing dates utilizing estimated market discount rates.

No definition available.