DERIVATIVE FINANCIAL INSTRUMENTS (Details 2) (Interest rate swaps on certificates of deposits, USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Derivatives
Notional amount terminated	$ 3,600,000ewbc_DerivativeNotionalAmountTerminated
Interest Expense
Net gains (losses) recognized in the Income Statement
Gains (losses) recognized on interest rate swaps	3,048,000	2,704,000
Net amount recognized on fair value hedges (ineffective portion)	353,000	(233,000)
Reduction in interest expense recognized on interest rate swaps	920,000	1,824,000
Interest Expense \| Certificates of deposits
Net gains (losses) recognized in the Income Statement
Gains (losses) recognized on certificates of deposit	$ (2,695,000)	$ (2,937,000)

Aggregate notional amount of derivatives terminated during the period. Expressed as an absolute value.

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- Definition

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

+ References

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- Definition

Amount of gain (loss) from the ineffectiveness of the hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (d)(1)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

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-Section 50

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Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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