Note 21 - Condensed Financial Information of Cathay General Bancorp - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash Flows from Operating Activities
Net income	$ 354,124	$ 360,642	$ 298,304
Gain on equity securities	(18,248)	(392)	1,426
Write-downs on venture capital and other investments	86,616	42,065	45,447
Net change in accrued interest receivable and other assets	(54,369)	(80,411)	(34,196)
Net change in other liabilities	(24,429)	107,467	2,403
Net cash provided by operating activities	384,742	467,390	334,317
Cash Flows from Investing Activities
Net cash used for investing activities	(1,477,080)	(1,849,433)	(859,924)
Cash Flows from Financing Activities
Cash dividends paid	(98,638)	(100,955)	(99,322)
Taxes paid related to net share settlement of RSUs	(4,490)	(2,905)	(2,632)
Purchase of treasury stock	(16,667)	(141,316)	(167,104)
Net cash provided by financing activities	758,737	94,741	1,554,233
(Decrease)/increase in cash, cash equivalents, and restricted cash	(333,601)	(1,287,302)	1,028,626
Cash, cash equivalents, and restricted cash, beginning of the year	1,162,402	2,449,704	1,421,078
Cash, cash equivalents, and restricted cash, end of the period	828,801	1,162,402	2,449,704
Parent Company [Member]
Cash Flows from Operating Activities
Net income	354,124	360,642	298,304
Equity in undistributed earnings of subsidiaries	(214,575)	(133,433)	(72,338)
Gain on equity securities	(17,977)	(733)	(122)
Write-downs on venture capital and other investments	179	268	73
Loss/(gain) in fair value of warrants	50	(27)	0
Stock issued to directors as compensation	850	849	850
Net change in accrued interest receivable and other assets	5,216	(434)	1,918
Net change in other liabilities	(2,371)	8,531	4,934
Net cash provided by operating activities	125,496	235,663	233,619
Cash Flows from Investing Activities
Venture capital and other investments	168	(5)	357
Net cash used for investing activities	168	(5)	357
Cash Flows from Financing Activities
Cash dividends paid	(98,638)	(100,955)	(99,322)
Proceeds from shares issued under the Dividend Reinvestment Plan	3,491	3,720	3,563
Taxes paid related to net share settlement of RSUs	(4,490)	(2,905)	(2,632)
Purchase of treasury stock	(16,667)	(141,316)	(167,104)
Net cash provided by financing activities	(116,304)	(241,456)	(265,495)
(Decrease)/increase in cash, cash equivalents, and restricted cash	9,360	(5,798)	(31,519)
Cash, cash equivalents, and restricted cash, beginning of the year	14,902	20,700	52,219
Cash, cash equivalents, and restricted cash, end of the period	$ 24,262	$ 14,902	$ 20,700