Condensed Consolidated Statements of Operations and Comprehensive Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
INTEREST AND DIVIDEND INCOME
Loans receivable, including loan fees	$ 90,024	$ 92,590	$ 269,486	$ 272,940
Investment securities- taxable	15,157	20,304	50,046	65,274
Investment securities- nontaxable	1,036	1,054	3,127	3,165
Federal Home Loan Bank stock	57	38	190	134
Federal funds sold and securities purchased under agreements to resell	2	33	18	81
Deposits with banks	471	360	1,596	901
Total interest and dividend income	106,747	114,379	324,463	342,495
INTEREST EXPENSE
Time deposits of $100,000 or more	7,970	10,496	26,152	32,115
Other deposits	3,261	4,777	11,045	15,871
Securities sold under agreements to repurchase	13,734	14,840	42,987	45,903
Advances from Federal Home Loan Bank	74	2,101	196	10,592
Long-term debt	1,291	1,208	3,895	3,630
Short-term borrowings		4		11
Total interest expense	26,330	33,426	84,275	108,122
Net interest income before provision for credit losses	80,417	80,953	240,188	234,373
Provision/(credit) for loan losses		9,000	(9,000)	25,000
Net interest income after provision for loan losses	80,417	71,953	249,188	209,373
NON-INTEREST INCOME
Securities gains, net	8,652	8,833	13,241	20,243
Letters of credit commissions	1,728	1,440	4,873	4,113
Depository service fees	1,342	1,341	4,114	4,101
Other operating income	3,900	5,213	12,077	13,449
Total non-interest income	15,622	16,827	34,305	41,906
NON-INTEREST EXPENSE
Salaries and employee benefits	18,451	17,481	58,426	53,411
Occupancy expense	3,853	3,714	10,926	10,709
Computer and equipment expense	2,340	2,139	7,194	6,437
Professional services expense	5,273	4,846	15,224	13,534
FDIC and State assessments	2,094	2,642	6,554	9,864
Marketing expense	519	908	3,408	2,420
Other real estate owned expense	1,794	6,120	13,548	8,603
Operations of affordable housing investments, net	476	2,102	4,387	6,055
Amortization of core deposit intangibles	1,404	1,461	4,265	4,402
Cost associated with debt redemption	3,450	4,540	6,200	18,527
Other operating expense	8,190	2,430	12,925	7,614
Total non-interest expense	47,844	48,383	143,057	141,576
Income before income tax expense	48,195	40,397	140,436	109,703
Income tax expense	17,686	14,162	50,852	36,802
Net income	30,509	26,235	89,584	72,901
Less: net income attributable to noncontrolling interest	151	151	452	452
Net income attributable to Cathay General Bancorp	30,358	26,084	89,132	72,449
Dividends on preferred stock	(4,123)	(4,111)	(12,361)	(12,323)
Net income attributable to common stockholders	26,235	21,973	76,771	60,126
Other comprehensive income, net of tax
Unrealized holding gain/(loss) arising during the period	10,650	(4,753)	18,353	7,264
Less: reclassification adjustments included in net income	5,015	5,120	7,674	11,733
Total other comprehensive gain/(loss), net of tax	5,635	(9,873)	10,679	(4,469)
Total comprehensive income	$ 35,993	$ 16,211	$ 99,811	$ 67,980
Net income per common share:
Basic (in Dollars per share)	$ 0.33	$ 0.28	$ 0.98	$ 0.76
Diluted (in Dollars per share)	$ 0.33	$ 0.28	$ 0.98	$ 0.76
Cash dividends paid per common share (in Dollars per share)	$ 0.01	$ 0.01	$ 0.03	$ 0.03
Average common shares outstanding
Basic (in Shares)	78,729,272	78,640,308	78,706,150	78,628,477
Diluted (in Shares)	78,731,180	78,641,142	78,711,235	78,637,977