SIGNIFICANT ACCOUNTING POLICIES (Details)	3 Months Ended
Mar. 31, 2012
Recent accounting standards
Minimum percentage of likelihood to determine that it is more likely than not	50.00%

Represents the minimum percentage of likelihood to determine that it is more likely than not that the fair value of a reporting unit is less than its carrying amount.

No definition available.

Name:	ewbc_MoreLikelyThanNotMinimumLikelihoodPercentage
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration