Note 20 - Condensed Financial Information of Cathay General Bancorp (Details) - Balance Sheets (Parentheticals) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in Dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000us-gaap_CommonStockSharesAuthorized	100,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued	84,022,118us-gaap_CommonStockSharesIssued	83,797,434us-gaap_CommonStockSharesIssued
Common stock, shares outstanding	79,814,553us-gaap_CommonStockSharesOutstanding	79,589,869us-gaap_CommonStockSharesOutstanding
Treasury stock, shares	4,207,565us-gaap_TreasuryStockShares	4,207,565us-gaap_TreasuryStockShares
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in Dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	84,022,118	83,797,434
Common stock, shares outstanding	79,814,553	79,589,869
Treasury stock, shares	4,207,565	4,207,565

Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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