Note 21 - Condensed Financial Information of Cathay General Bancorp - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	May 31, 2014
Assets
Cash pledged as margin for interest rate swaps	$ 88,900	$ 24,300
Equity securities	22,158	22,319
Other assets	250,069	195,403
Total assets	21,947,976	20,886,723
Liabilities
Junior subordinated debt	119,136	119,136			$ 119,100
Other liabilities	307,031	180,543
Total liabilities	19,473,936	18,440,472
Commitments and contingencies
Stockholders' equity
Common stock, $0.01 par value, 100,000,000 shares authorized, 91,090,614 issued and 72,742,151 outstanding at December 31, 2022, and 90,871,860 issued and 75,750,862 outstanding at December 31, 2021.	911	909
Additional paid-in-capital	981,119	972,474
Accumulated other comprehensive income/(loss), net	(102,295)	(3,065)
Retained earnings	2,244,856	1,985,168
Treasury stock, at cost (18,348,463 shares at December 31, 2022, and 15,120,998 shares at December 31, 2021)	(650,551)	(509,235)
Total equity	2,474,040	2,446,251	$ 2,418,144	$ 2,294,283
Total liabilities and equity	21,947,976	20,886,723
Parent Company [Member]
Assets
Cash	14,902	19,629
Cash pledged as margin for interest rate swaps	0	1,071
Short-term certificates of deposit	334	333
Equity securities	16,360	15,627
Other assets	4,385	4,691
Total assets	2,603,011	2,573,008
Liabilities
Junior subordinated debt	119,136	119,136
Other liabilities	9,835	7,621
Total liabilities	128,971	126,757
Commitments and contingencies
Stockholders' equity
Common stock, $0.01 par value, 100,000,000 shares authorized, 91,090,614 issued and 72,742,151 outstanding at December 31, 2022, and 90,871,860 issued and 75,750,862 outstanding at December 31, 2021.	911	909
Additional paid-in-capital	981,119	972,474
Accumulated other comprehensive income/(loss), net	(102,295)	(3,065)
Retained earnings	2,244,856	1,985,168
Treasury stock, at cost (18,348,463 shares at December 31, 2022, and 15,120,998 shares at December 31, 2021)	(650,551)	(509,235)
Total equity	2,474,040	2,446,251
Total liabilities and equity	2,603,011	2,573,008
Parent Company [Member] | Bank Subsidiaries [Member]
Assets
Investment in subsidiaries	2,566,266	2,530,850
Non Bank Subsidiaries [Member] | Bank Subsidiaries [Member]
Assets
Investment in subsidiaries	$ 764	$ 807