SECURITIES PURCHASED UNDER RESALE AGREEMENTS AND SOLD UNDER REPURCHASE AGREEMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Resale agreements
Total	$ 2,050,000	$ 1,425,000
Weighted average interest rates	1.61%	1.55%
Maturities in 2016	$ 950,000
Maturities in 2017	50,000
Maturities in 2018	50,000
Maturities in 2019	0
Maturities in 2020	100,000
Maturities thereafter	$ 900,000

Weighted average interest rate on the amount to be repaid by the counterparty to the resale agreement.

No definition available.

Name:	ewbc_AssetsPurchasedUnderAgreementsToResellInterestRate
Namespace Prefix:	ewbc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of maturities, in year five following the date of the latest balance sheet, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

No definition available.

+ Details

Name:	ewbc_SecuritiesPurchasedUnderAgreementsToResellGrossMaturitiesInYearFive
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of maturities, in year four following the date of the latest balance sheet, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

No definition available.

+ Details

Name:	ewbc_SecuritiesPurchasedUnderAgreementsToResellGrossMaturitiesInYearFour
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of maturities, in year one following the date of the latest balance sheet, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

No definition available.

+ Details

Name:	ewbc_SecuritiesPurchasedUnderAgreementsToResellGrossMaturitiesInYearOne
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of maturities, in year six and thereafter following the date of the latest balance sheet, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

No definition available.

+ Details

Name:	ewbc_SecuritiesPurchasedUnderAgreementsToResellGrossMaturitiesInYearSixAndThereafter
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of maturities, in year three following the date of the latest balance sheet, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

No definition available.

+ Details

Name:	ewbc_SecuritiesPurchasedUnderAgreementsToResellGrossMaturitiesInYearThree
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of maturities, in year two following the date of the latest balance sheet, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

No definition available.

+ Details

Name:	ewbc_SecuritiesPurchasedUnderAgreementsToResellGrossMaturitiesInYearTwo
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_SecuritiesPurchasedUnderAgreementsToResellAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313

+ Details

Name:	us-gaap_SecuritiesPurchasedUnderAgreementsToResellGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant