BASIS OF PRESENTATION (Details)	3 Months Ended
Mar. 31, 2015 entity trust	Mar. 31, 2014 entity
BASIS OF PRESENTATION
Number of wholly owned subsidiaries that are statutory business trusts ("the Trusts")	6
Number of acquisitions	0us-gaap_NumberOfBusinessesAcquired	1us-gaap_NumberOfBusinessesAcquired

Represents the number of wholly owned subsidiaries of the entity that are statutory business trusts, which are not consolidated.

No definition available.

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