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Note 20 - Condensed Financial Information of Cathay General Bancorp (Details) - Balance Sheets (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014 | May 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
--- | --- | --- | --- | --- | ---
Assets |  |  |  |  |
Cash | $ 176,830 us-gaap_CashAndCashEquivalentsAtCarryingValue |  | $ 153,747 us-gaap_CashAndCashEquivalentsAtCarryingValue | $ 144,909 us-gaap_CashAndCashEquivalentsAtCarryingValue | $ 117,888 us-gaap_CashAndCashEquivalentsAtCarryingValue
Short-term certificates of deposit | 489,614 us-gaap_ShortTermInvestments |  | 516,938 us-gaap_ShortTermInvestments |  |
Securities available for sale | 1,318,935 us-gaap_AvailableForSaleSecurities |  | 1,586,668 us-gaap_AvailableForSaleSecurities |  |
Other assets | 143,106 us-gaap_OtherAssets |  | 190,634 us-gaap_OtherAssets |  |
Total assets | 11,516,846 us-gaap_Assets |  | 10,989,286 us-gaap_Assets |  |
Liabilities |  |  |  |  |
Junior subordinated debt | 119,136 us-gaap_JuniorSubordinatedNotes | 119,100 us-gaap_JuniorSubordinatedNotes |  |  |
Other liabilities | 80,772 us-gaap_OtherLiabilities |  | 55,418 us-gaap_OtherLiabilities |  |
Total liabilities | 9,913,958 us-gaap_Liabilities |  | 9,530,315 us-gaap_Liabilities |  |
Stockholders' equity |  |  |  |  |
Common stock, $0.01 par value, 100,000,000 shares authorized, 84,022,118 issued and 79,814,553 outstanding at December 31, 2014, and 83,797,434 issued and 79,589,869 outstanding at December 31, 2013 | 840 us-gaap_CommonStockValue |  | 838 us-gaap_CommonStockValue |  |
Additional paid-in-capital | 789,519 us-gaap_AdditionalPaidInCapital |  | 784,489 us-gaap_AdditionalPaidInCapital |  |
Accumulated other comprehensive loss, net | (5,569)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax |  | (29,729)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax | 465 us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax |
Retained earnings | 943,834 us-gaap_RetainedEarningsAccumulatedDeficit |  | 829,109 us-gaap_RetainedEarningsAccumulatedDeficit |  |
Treasury stock, at cost (4,207,565 shares at December 31, 2014, and at December 31, 2013) | (125,736)us-gaap_TreasuryStockValue |  | (125,736)us-gaap_TreasuryStockValue |  |
Total liabilities and stockholders' equity | 11,516,846 us-gaap_LiabilitiesAndStockholdersEquity |  | 10,989,286 us-gaap_LiabilitiesAndStockholdersEquity |  |
Bank Subsidiaries [Member] | Parent Company [Member] |  |  |  |  |
Assets |  |  |  |  |
Investment in subsidiaries | 1,666,238 us-gaap_EquityMethodInvestmentAggregateCost / invest_InvestmentAxis = caty_BankSubsidiariesMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 1,525,459 us-gaap_EquityMethodInvestmentAggregateCost / invest_InvestmentAxis = caty_BankSubsidiariesMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Non-Bank Subsidiaries [Member] | Parent Company [Member] |  |  |  |  |
Assets |  |  |  |  |
Investment in subsidiaries | 2,631 us-gaap_EquityMethodInvestmentAggregateCost / invest_InvestmentAxis = caty_NonBankSubsidiariesMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 2,536 us-gaap_EquityMethodInvestmentAggregateCost / invest_InvestmentAxis = caty_NonBankSubsidiariesMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Parent Company [Member] |  |  |  |  |
Assets |  |  |  |  |
Cash | 7,420 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 1,835 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Cash pledged as margin for interest rate swaps | 7,465 us-gaap_MarginDepositAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |  |
Short-term certificates of deposit | 23,203 us-gaap_ShortTermInvestments / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 38,000 us-gaap_ShortTermInvestments / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Securities available for sale | 10,244 us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 11,404 us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Other assets | 9,541 us-gaap_OtherAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 1,462 us-gaap_OtherAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Total assets | 1,726,742 us-gaap_Assets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 1,580,696 us-gaap_Assets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Liabilities |  |  |  |  |
Junior subordinated debt | 119,136 us-gaap_JuniorSubordinatedNotes / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 121,136 us-gaap_JuniorSubordinatedNotes / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Other liabilities | 4,718 us-gaap_OtherLiabilities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 589 us-gaap_OtherLiabilities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Total liabilities | 123,854 us-gaap_Liabilities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 121,725 us-gaap_Liabilities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Stockholders' equity |  |  |  |  |
Common stock, $0.01 par value, 100,000,000 shares authorized, 84,022,118 issued and 79,814,553 outstanding at December 31, 2014, and 83,797,434 issued and 79,589,869 outstanding at December 31, 2013 | 840 us-gaap_CommonStockValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 838 us-gaap_CommonStockValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Additional paid-in-capital | 789,519 us-gaap_AdditionalPaidInCapital / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 784,489 us-gaap_AdditionalPaidInCapital / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Accumulated other comprehensive loss, net | (5,569)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (29,729)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Retained earnings | 943,834 us-gaap_RetainedEarningsAccumulatedDeficit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 829,109 us-gaap_RetainedEarningsAccumulatedDeficit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Treasury stock, at cost (4,207,565 shares at December 31, 2014, and at December 31, 2013) | (125,736)us-gaap_TreasuryStockValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (125,736)us-gaap_TreasuryStockValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Total stockholders' equity | 1,602,888 us-gaap_StockholdersEquity / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 1,458,971 us-gaap_StockholdersEquity / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Total liabilities and stockholders' equity | $ 1,726,742 us-gaap_LiabilitiesAndStockholdersEquity / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | $ 1,580,696 us-gaap_LiabilitiesAndStockholdersEquity / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |

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- Definition Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e681-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 + Details
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- Definition Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders. Includes adjustments to additional paid in capital. Some examples of such adjustments include recording the issuance of debt with a beneficial conversion feature and certain tax consequences of equity instruments awarded to employees. Use this element for the aggregate amount of additional paid-in capital associated with common and preferred stock. For additional paid-in capital associated with only common stock, use the element additional paid in capital, common stock. For additional paid-in capital associated with only preferred stock, use the element additional paid in capital, preferred stock. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.30(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.18) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 18 -Article 5 + Details
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- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 + Details
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- Definition Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + Details
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- Definition Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16(a)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 13, 16 -Article 9 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The cumulative amount of the reporting entity's undistributed earnings or deficit. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.31(a)(3)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 4.E) -URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section E Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29-31) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 + Details
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