Note 20 - Condensed Financial Information of Cathay General Bancorp (Details) - Statements of Operations (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Income Statements, Captions [Line Items]
Interest income	$ 101,621	$ 102,462	$ 100,862	$ 102,051	$ 105,281	$ 106,747	$ 107,581	$ 110,135
Interest expense	19,659	19,854	20,868	21,919	24,216	26,330	28,461	29,484	82,300	108,491	139,881
Non-interest income/(loss)	8,345	16,720	20,361	14,881	12,202	15,622	9,852	8,831	60,307	46,507	50,892
Non-interest expense	40,319	50,670	53,716	49,128	49,532	47,844	47,342	47,871	193,833	192,589	185,566
Income tax benefit	17,946	19,029	16,573	16,887	15,276	17,686	16,619	16,547	70,435	66,128	51,261
Loss before undistributed earnings of subsidiaries	49,988	51,658	46,639	45,885	43,735	48,195	46,630	45,611	194,170	184,171	152,016
Net income	32,042	32,629	30,066	28,998	28,459	30,509	30,011	29,064	123,143	117,438	100,150
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Cash dividends from Cathay Bank									138,030	154,700
Interest income									157	196	259
Interest expense									2,994	3,228	3,038
Non-interest income/(loss)									434	3,718	286
Non-interest expense									2,443	2,064	1,548
Income/(loss) before income tax benefit									133,184	153,322	(4,041)
Income tax benefit									(2,037)	(579)	(1,699)
Loss before undistributed earnings of subsidiaries									135,221	153,901	(2,342)
Distributions less (more) than earnings of subsidiaries									(12,078)	(36,463)	102,492
Net income									$ 123,143	$ 117,438	$ 100,150