Condensed Consolidated Statements of Operations and Comprehensive Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
INTEREST AND DIVIDEND INCOME
Loans receivable, including loan fees	$ 88,761	$ 89,792	$ 179,462	$ 180,350
Investment securities- taxable	17,166	23,116	34,889	44,970
Investment securities- nontaxable	1,039	1,055	2,091	2,111
Federal Home Loan Bank stock	67	49	133	96
Federal funds sold and securities purchased under agreements to resell	11	7	16	48
Deposits with banks	537	320	1,125	541
Total interest and dividend income	107,581	114,339	217,716	228,116
INTEREST EXPENSE
Time deposits of $100,000 or more	8,642	10,894	18,182	21,619
Other deposits	3,868	5,374	7,784	11,094
Securities sold under agreements to repurchase	14,598	14,892	29,253	31,063
Advances from Federal Home Loan Bank	69	3,642	122	8,491
Long-term debt	1,284	1,216	2,604	2,422
Short-term borrowings		6		7
Total interest expense	28,461	36,024	57,945	74,696
Net interest income before provision for credit losses	79,120	78,315	159,771	153,420
Provision/(credit) for loan losses	(5,000)	10,000	(9,000)	16,000
Net interest income after provision for loan losses	84,120	68,315	168,771	137,420
NON-INTEREST INCOME
Securities gains, net	2,374	5,178	4,589	11,410
Letters of credit commissions	1,619	1,395	3,145	2,673
Depository service fees	1,383	1,399	2,772	2,760
Other operating income	4,476	4,481	8,177	8,236
Total non-interest income	9,852	12,453	18,683	25,079
NON-INTEREST EXPENSE
Salaries and employee benefits	20,097	17,659	39,975	35,930
Occupancy expense	3,489	3,457	7,073	6,995
Computer and equipment expense	2,391	2,115	4,854	4,298
Professional services expense	5,209	4,959	9,951	8,688
FDIC and State assessments	1,971	2,905	4,460	7,222
Marketing expense	1,483	817	2,889	1,512
Other real estate owned expense	7,061	2,262	11,754	2,483
Operations of affordable housing investments, net	1,951	1,977	3,911	3,953
Amortization of core deposit intangibles	1,404	1,460	2,861	2,941
Cost associated with debt redemption		5,176	2,750	13,987
Other operating expense	2,286	2,623	4,735	5,184
Total non-interest expense	47,342	45,410	95,213	93,193
Income before income tax expense	46,630	35,358	92,241	69,306
Income tax expense	16,619	10,906	33,166	22,640
Net income	30,011	24,452	59,075	46,666
Less: net income attributable to noncontrolling interest	150	150	301	301
Net income attributable to Cathay General Bancorp	29,861	24,302	58,774	46,365
Dividends on preferred stock	(4,121)	(4,107)	(8,238)	(8,212)
Net income attributable to common stockholders	25,740	20,195	50,536	38,153
Other comprehensive income, net of tax
Unrealized holding gain arising during the period	2,225	11,974	7,704	12,017
Less: reclassification adjustments included in net income	1,376	3,001	2,660	6,613
Total other comprehensive gain, net of tax	849	8,973	5,044	5,404
Total comprehensive income	$ 30,710	$ 33,275	$ 63,818	$ 51,769
Net income per common share:
Basic (in Dollars per share)	$ 0.33	$ 0.26	$ 0.64	$ 0.49
Diluted (in Dollars per share)	$ 0.33	$ 0.26	$ 0.64	$ 0.49
Cash dividends paid per common share (in Dollars per share)	$ 0.01	$ 0.01	$ 0.02	$ 0.02
Average common shares outstanding
Basic (in Shares)	78,710,279	78,635,324	78,694,462	78,622,464
Diluted (in Shares)	78,712,172	78,637,108	78,701,152	78,636,369