SUBSEQUENT EVENTS (Details) (USD $) In Millions, except Per Share data	Jul. 20, 2011 Preferred Stock, Series A [Member] Dividend Approved for Payment [Member]	Jul. 20, 2011 Common Stock [Member] Dividend Declared [Member]	Aug. 03, 2011 Loan Sale [Member]	Apr. 26, 2011 Common Stock [Member]
Dividend Payout [Abstract]
Dividend declaration date	2011-07-20	2011-07-20		2011-04-26
Dividend per share (in dollars per share)	$ 20.00	$ 0.05		$ 0.05
Dividend payment date	2011-08-01	2011-08-24		2011-05-10
Dividend record date	2011-07-15	2011-08-10		2011-05-24
Loan Sale [Abstract]
Student loans sold			$ 235
Gain on sale of student loans			$ 4.7

Name:	ewbc_DividendPayoutAbstract
Namespace Prefix:	ewbc
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The day, month and year (YYYY-MM-DD) that the dividend to be paid was declared.

+ Details

Name:	ewbc_DividendsPayableDateDeclared
Namespace Prefix:	ewbc
Data Type:	invest:dateStringItemType
Balance Type:	na
Period Type:	instant

- Definition

The date as of when a holder must own the stock to be entitled to the dividend.

+ Details

Name:	ewbc_DividendsPayableDateOfRecord
Namespace Prefix:	ewbc
Data Type:	invest:dateStringItemType
Balance Type:	na
Period Type:	instant

- Definition

The day, month, and year (YYYY-MM-DD) that the dividend declared as of or prior to the financial reporting date will be paid in the subsequent period.

+ Details

Name:	ewbc_DividendsPayableDateToBePaid
Namespace Prefix:	ewbc
Data Type:	invest:dateStringItemType
Balance Type:	na
Period Type:	instant

- Definition

The gains (losses) included in earning that represent the difference between the sale price and the carrying value of student loans. This element refers to the gain (loss) and not to the cash proceeds of the sale.

+ Details

Name:	ewbc_GainLossOnSalesOfStudentLoans
Namespace Prefix:	ewbc
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	ewbc_LoanSaleAbstract
Namespace Prefix:	ewbc
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of student loans sold in a loan sale transaction with a major investment brokerage firm.

+ Details

Name:	ewbc_StudentLoansSold
Namespace Prefix:	ewbc
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 32
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

Name:	us-gaap_DividendsPayableAmountPerShare
Namespace Prefix:	us-gaap
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant