COMMITMENTS AND CONTINGENCIES (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Undisbursed Loan Commitments
Credit Extensions
Loan	$ 2,750,000,000	$ 2,610,000,000
Commercial and Standby Letters of Credit
Credit Extensions
Commercial and standby letters of credit issued	$ 994,400,000	$ 998,700,000

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.

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