Note 21 - Condensed Financial Information of Cathay General Bancorp - Balance Sheets (Details) (Parentheticals) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	91,090,614	90,871,860
Common stock, shares outstanding (in shares)	72,742,151	75,750,862
Treasury stock shares (in shares)	18,348,463	15,120,998
Parent Company [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	91,090,614	90,871,860
Common stock, shares outstanding (in shares)	72,742,151	75,750,862
Treasury stock shares (in shares)	18,348,463	15,120,998