BASIS OF PRESENTATION (Details)	Sep. 30, 2012 trust
BASIS OF PRESENTATION
Number of wholly owned subsidiaries that are statutory business trusts	7

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