COMMITMENTS AND CONTINGENCIES (Details) (USD $) In Billions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Undisbursed Loan Commitments
Credit Extensions
Loan	$ 2.57	$ 2.19
Commercial and Standby Letters of Credit
Credit Extensions
Commercial and standby letters of credit issued	$ 2.14	$ 1.64

Reflects the amount of cash required to fully fund agreements to provide advances to borrowers and lessees at fixed and variable interest rates.

No definition available.

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