Note 19 - Condensed Financial Information of Cathay General Bancorp - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flows from Operating Activities
Net income	$ 298,304	$ 228,860	$ 279,135
Write-downs on venture capital and other investments	45,447	58,131	39,898
Net change in accrued interest receivable and other assets	(34,196)	(21,247)	6,163
Net change in other liabilities	2,403	(18,948)	21,061
Net cash provided by operating activities	334,317	319,955	434,979
Cash Flows from Investing Activities
Net cash used for investing activities	(859,924)	(242,204)	(1,381,674)
Cash Flows from Financing Activities
Repayment of long-term debt	0	(7,663)	(81,065)
Cash dividends paid	(99,322)	(98,688)	(99,131)
Taxes paid related to net share settlement of RSUs	(2,632)	(1,911)	(2,311)
Purchase of treasury stock	(167,104)	(23,593)	(36,301)
Net cash provided by financing activities	1,554,233	749,549	940,183
Increase/(Decrease) in cash, cash equivalents, and restricted cash	1,028,626	827,300	(6,512)
Cash, cash equivalents, and restricted cash, beginning of the year	1,421,078	593,778	600,290
Cash, cash equivalents, and restricted cash, end of the period	2,449,704	1,421,078	593,778
Parent Company [Member]
Cash Flows from Operating Activities
Net income	298,304	228,860	279,135
Equity in undistributed earnings of subsidiaries	(72,338)	(90,306)	(44,860)
Loss/(gain) on equity securities	(122)	641	(4,414)
Write-downs on venture capital and other investments	73	107	105
Loss in fair value of warrants	0	18	145
Stock issued to directors as compensation	850	800	749
Net change in accrued interest receivable and other assets	1,918	(1,182)	125
Net change in other liabilities	4,934	(9,853)	(832)
Net cash provided by operating activities	233,619	129,085	230,153
Cash Flows from Investing Activities
Proceeds from liquidation of subsidiary	0	2,399	0
Proceeds from sale of equity securities	0	3,112	2,829
Venture capital and other investments	357	116	399
Net cash used for investing activities	357	5,627	3,228
Cash Flows from Financing Activities
Repayment of long-term debt	0	(7,644)	(81,065)
Cash dividends paid	(99,322)	(98,688)	(99,131)
Proceeds from shares issued under the Dividend Reinvestment Plan	3,563	9,777	3,366
Taxes paid related to net share settlement of RSUs	(2,632)	(1,911)	(2,311)
Purchase of treasury stock	(167,104)	(23,593)	(36,301)
Net cash provided by financing activities	(265,495)	(122,059)	(215,442)
Increase/(Decrease) in cash, cash equivalents, and restricted cash	(31,519)	12,653	17,939
Cash, cash equivalents, and restricted cash, beginning of the year	52,219	39,566	21,627
Cash, cash equivalents, and restricted cash, end of the period	$ 20,700	$ 52,219	$ 39,566