Note 21 - Condensed Financial Information of Cathay General Bancorp - Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Interest expense	$ 117,584	$ 68,756	$ 148,464
Non-interest expense	303,432	286,523	283,465
Income before income tax expense	472,536	381,843	253,965
Income tax expense	111,894	83,539	25,105
Net income	360,642	298,304	228,860
Parent Company [Member]
Cash dividends from Cathay Bank	232,773	230,000	146,000
Interest income	30	36	49
Interest expense	5,560	5,773	5,906
Non-interest Income/(loss)	1,018	3,117	(435)
Non-interest expense	3,937	3,224	4,846
Income before income tax expense	224,324	224,156	134,862
Income tax expense	(2,885)	(1,810)	(3,692)
Income before undistributed earnings of subsidiaries	227,209	225,966	138,554
Undistributed earnings of subsidiary	133,433	72,338	90,306
Net income	$ 360,642	$ 298,304	$ 228,860