Note 21 - Condensed Financial Information of Cathay General Bancorp - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	May 31, 2014
Assets
Equity securities	$ 40,406	$ 22,158
Other assets	267,762	250,069
Total assets	23,081,534	21,947,976
Liabilities
Junior subordinated debt	119,136	119,136			$ 119,100
Other liabilities	306,528	307,031
Total liabilities	20,344,959	19,473,936
Commitments and contingencies
Stockholders' equity
Common stock, $0.01 par value, 100,000,000 shares authorized, 91,392,480 issued and 72,668,927 outstanding at December 31, 2023, and 91,090,614 issued and 72,742,151 outstanding at December 31, 2022	914	911
Additional paid-in-capital	987,953	981,119
Accumulated other comprehensive income loss, net	(85,416)	(102,295)
Retained earnings	2,500,341	2,244,855
Total equity	2,736,575	2,474,040	$ 2,446,251	$ 2,418,144
Total liabilities and equity	23,081,534	21,947,976
Parent Company [Member]
Assets
Cash	24,262	14,902
Short-term certificates of deposit	335	334
Equity securities	34,441	16,360
Other assets	3,896	4,385
Total assets	2,869,469	2,603,011
Liabilities
Junior subordinated debt	119,136	119,136
Other liabilities	13,758	9,835
Total liabilities	132,894	128,971
Commitments and contingencies
Stockholders' equity
Common stock, $0.01 par value, 100,000,000 shares authorized, 91,392,480 issued and 72,668,927 outstanding at December 31, 2023, and 91,090,614 issued and 72,742,151 outstanding at December 31, 2022	914	911
Additional paid-in-capital	987,953	981,119
Accumulated other comprehensive income loss, net	(85,416)	(102,295)
Retained earnings	2,500,341	2,244,855
Treasury stock, at cost (18,723,553 shares at December 31, 2023, and 18,348,463 shares at December 31, 2022)	(667,217)	(650,550)
Total equity	2,736,575	2,474,040
Total liabilities and equity	2,869,469	2,603,011
Parent Company [Member] | Bank Subsidiaries [Member]
Assets
Investment in subsidiaries	2,806,467	2,566,266
Parent Company [Member] | Non Bank Subsidiaries [Member]
Assets
Investment in subsidiaries	$ 68	$ 764