Note 21 - Condensed Financial Information of Cathay General Bancorp - Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest expense	$ 500,476	$ 117,584	$ 68,756
Non-interest expense	380,478	303,432	286,523
Income before income tax expense	403,582	472,536	381,843
Income tax expense/(benefit)	49,458	111,894	83,539
Net income	354,124	360,642	298,304
Parent Company [Member]
Cash dividends from Cathay Bank	134,000	232,773	230,000
Interest income	44	30	36
Interest expense	6,480	5,560	5,773
Non-interest Income	17,757	1,018	3,117
Non-interest expense	4,065	3,937	3,224
Income before income tax expense	141,256	224,324	224,156
Income tax expense/(benefit)	1,707	(2,885)	(1,810)
Income before undistributed earnings of subsidiaries	139,549	227,209	225,966
Undistributed earnings of subsidiary	214,575	133,433	72,338
Net income	$ 354,124	$ 360,642	$ 298,304