Name:	ewbc_OtherComprehensiveIncomeLossReclassificationAdjustmentForSaleOrWriteDownOfSecuritiesIncludedInNetIncomeBeforeTax
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Other Comprehensive Income Loss, Reclassification Adjustment For Sale Or Write Down Of Securities Included In Net Income, Net of Tax

No definition available.

Name:	ewbc_OtherComprehensiveIncomeLossReclassificationAdjustmentForSaleOrWriteDownOfSecuritiesIncludedInNetIncomeNetOfTax
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Other Comprehensive Income Loss, Reclassification Adjustment For Sale Or Write Down Of Securities Included In Net Income, Tax

No definition available.

Name:	ewbc_OtherComprehensiveIncomeLossReclassificationAdjustmentForSaleOrWriteDownOfSecuritiesIncludedInNetIncomeTax
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount before tax and reclassification adjustments of other comprehensive income (loss) attributable to parent.

Name:	us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=124507222&loc=d3e1436-108581

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669686-108580

Name:	us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount, after tax, of adjustment from accumulated other comprehensive income (loss) for amortization of gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from transfer to investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669686-108580

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 10B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124260725&loc=SL120268667-111560

Name:	us-gaap_OciDebtSecuritiesAvailableForSaleTransferToHeldToMaturityAdjustmentFromAociForAmortizationOfGainLossAfterTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount, before tax, of adjustment from accumulated other comprehensive income (loss) for amortization of gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from transfer to investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 10B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124260725&loc=SL120268667-111560

Name:	us-gaap_OciDebtSecuritiesAvailableForSaleTransferToHeldToMaturityAdjustmentFromAociForAmortizationOfGainLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of tax expense (benefit) on adjustment from accumulated other comprehensive income (loss) for amortization of gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from transfer to investment in debt security measured at amortized cost (held-to-maturity).

Name:	us-gaap_OciDebtSecuritiesAvailableForSaleTransferToHeldToMaturityAdjustmentFromAociForAmortizationOfGainLossTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of tax expense (benefit) allocated to other comprehensive income (loss) before reclassification adjustment from accumulated other comprehensive income (loss).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124442407-227067

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e640-108580

Name:	us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

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

Amount before tax of other comprehensive income (loss) attributable to parent entity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4569616-111683

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4569643-111683

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684

Name:	us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

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

Amount after tax of other comprehensive income (loss) attributable to parent entity.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669625-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4569643-111683

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669619-108580

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4569616-111683

Name:	us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

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

Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4569643-111683

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4569616-111683

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684

Name:	us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount before tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

Name:	us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669686-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=124507222&loc=d3e1436-108581

Name:	us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124442407-227067

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 17A
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL34724391-108580