Basis of Presentation and Current Accounting Developments (Details)	Sep. 30, 2021 trust
Accounting Policies [Abstract]
Number of Wholly Owned Statutory Business Trusts	6

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