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REGULATORY REQUIREMENTS (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013
Actual |  |
Total Capital (to Risk-Weighted Assets), Amount | $ 2,753,598,000 us-gaap_Capital | $ 2,395,109,000 us-gaap_Capital
Tier I Capital (to Risk-Weighted Assets), Amount | 2,405,452,000 us-gaap_TierOneRiskBasedCapital | 2,102,476,000 us-gaap_TierOneRiskBasedCapital
Tier I Capital (to Average Assets), Amount | 2,405,452,000 us-gaap_TierOneLeverageCapital | 2,102,476,000 us-gaap_TierOneLeverageCapital
Total Capital (to Risk-Weighted Assets), Ratio (as a percent) | 12.60%us-gaap_CapitalToRiskWeightedAssets | 13.50%us-gaap_CapitalToRiskWeightedAssets
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent) | 11.00%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets | 11.90%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
Tier I Capital (to Average Assets), Ratio (as a percent) | 8.40%us-gaap_TierOneLeverageCapitalToAverageAssets | 8.60%us-gaap_TierOneLeverageCapitalToAverageAssets
For Capital Adequacy Purposes |  |
Total Capital (to Risk-Weighted Assets), Amount | 1,754,519,000 us-gaap_CapitalRequiredForCapitalAdequacy | 1,416,203,000 us-gaap_CapitalRequiredForCapitalAdequacy
Tier I Capital (to Risk-Weighted Assets), Amount | 877,259,000 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy | 708,102,000 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
Tier I Capital (to Average Assets), Amount | 1,140,045,000 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy | 976,596,000 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
Total Capital (to Risk-Weighted Assets), Ratio (as a percent) | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent) | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Tier I Capital (to Average Assets), Ratio (as a percent) | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
Regulatory Requirements - Additional Disclosure |  |
Minimum total consolidated assets for exclusion of trust preferred securities as Tier I regulatory capital | 15,000,000,000 ewbc_MinimumTotalConsolidatedAssetsForExclusionOfTrustPreferredSecuritiesAsTierIRegulatoryCapital |
Trust preferred securities as a percentage of the Company's Tier I capital | 3.10%ewbc_TrustPreferredSecuritiesAsPercentageOfTierICapital | 4.40%ewbc_TrustPreferredSecuritiesAsPercentageOfTierICapital
Minimum value of assets held by depository institutions and top-tier bank holding companies to be in compliance with the Basel III Capital Rules | 500,000,000 ewbc_MinimumValueOfAssetsHeldForRequirementInAccordanceWithBaselIIICapitalRules |
East West Bank |  |
Actual |  |
Total Capital (to Risk-Weighted Assets), Amount | 2,590,174,000 us-gaap_Capital / dei_LegalEntityAxis = ewbc_EastWestBankMember | 2,262,494,000 us-gaap_Capital / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Risk-Weighted Assets), Amount | 2,316,615,000 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = ewbc_EastWestBankMember | 2,041,894,000 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Average Assets), Amount | 2,316,615,000 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = ewbc_EastWestBankMember | 2,041,894,000 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = ewbc_EastWestBankMember
Total Capital (to Risk-Weighted Assets), Ratio (as a percent) | 11.80%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 12.90%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent) | 10.60%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 11.60%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Average Assets), Ratio (as a percent) | 8.20%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 8.40%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
For Capital Adequacy Purposes |  |
Total Capital (to Risk-Weighted Assets), Amount | 1,750,006,000 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = ewbc_EastWestBankMember | 1,407,944,000 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Risk-Weighted Assets), Amount | 875,003,000 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = ewbc_EastWestBankMember | 703,972,000 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Average Assets), Amount | 1,136,734,000 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = ewbc_EastWestBankMember | 973,958,000 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = ewbc_EastWestBankMember
Total Capital (to Risk-Weighted Assets), Ratio (as a percent) | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent) | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Average Assets), Ratio (as a percent) | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
To Be Well Capitalized Under Prompt Corrective Action Provisions |  |
Total Capital (to Risk-Weighted Assets), Amount | 2,187,508,000 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = ewbc_EastWestBankMember | 1,759,931,000 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Risk-Weighted Assets), Amount | 1,312,505,000 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = ewbc_EastWestBankMember | 1,055,958,000 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Average Assets), Amount | 1,420,917,000 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = ewbc_EastWestBankMember | 1,217,448,000 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = ewbc_EastWestBankMember
Total Capital (to Risk-Weighted Assets), Ratio (as a percent) | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent) | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
Tier I Capital (to Average Assets), Ratio (as a percent) | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = ewbc_EastWestBankMember
Reserve Requirement |  |
Daily average reserve requirement | $ 325,700,000 ewbc_DailyAverageReserveRequirement / dei_LegalEntityAxis = ewbc_EastWestBankMember | $ 218,500,000 ewbc_DailyAverageReserveRequirement / dei_LegalEntityAxis = ewbc_EastWestBankMember

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- Definition The amount of total capital as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47304-110998 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47080-110998 + Details
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- Definition The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
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- Definition The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Total Capital divided by risk weighted assets as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
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- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Tier 1 Leverage Capital divided by average assets as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Tier 1 Risk Based Capital as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The minimum amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
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- Definition The amount of Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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