Note 19 - Condensed Financial Information of Cathay General Bancorp - Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest expense	$ 68,756	$ 148,464	$ 194,361
Non-interest expense	286,523	283,465	277,288
Income before income tax expense	381,843	253,965	349,369
Income tax expense	83,539	25,105	70,234
Net income	298,304	228,860	279,135
Parent Company [Member]
Cash dividends from Cathay Bank	230,000	146,000	238,998
Interest income	36	49	90
Interest expense	5,773	5,906	8,415
Non-interest Income/(loss)	3,117	(435)	4,634
Non-interest expense	3,224	4,846	3,491
Income before income tax expense	224,156	134,862	231,816
Income tax expense	(1,810)	(3,692)	(2,459)
Income before undistributed earnings of subsidiaries	225,966	138,554	234,275
Undistributed earnings of subsidiary	72,338	90,306	44,860
Net income	$ 298,304	$ 228,860	$ 279,135