Consolidated Statements of Operations and Comprehensive Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
INTEREST AND DIVIDEND INCOME
Loan receivable	$ 390,440	$ 359,959	$ 360,643
Investment securities- taxable	24,237	43,412	62,395
Investment securities- nontaxable		995	4,161
Federal Home Loan Bank stock	1,974	1,480	485
Federal funds sold and securities purchased under agreement to resell			18
Deposits with banks	1,996	1,150	2,042
Total interest and dividend income	418,647	406,996	429,744
INTEREST EXPENSE
Time deposits of $100,000 or more	27,465	27,211	33,441
Other deposits	18,304	13,178	13,932
Interest on securities sold under agreements to repurchase	24,685	37,692	55,699
Advances from the Federal Home Loan Bank	945	528	270
Long-term debt	4,467	3,691	5,149
Total interest expense	75,866	82,300	108,491
Net interest income before provision for credit losses	342,781	324,696	321,253
(Reversal)/provision for credit losses	(10,800)	(3,000)	(9,000)
Net interest income after provision for credit losses	353,581	327,696	330,253
NON-INTEREST INCOME
Securities gains, net	6,748	27,362	18,026
Letters of credit commissions	6,043	6,281	6,316
Depository service fees	5,288	5,701	5,453
Other operating income	22,448	20,963	16,712
Total non-interest income	40,527	60,307	46,507
NON-INTEREST EXPENSE
Salaries and employee benefits	89,893	88,276	78,377
Occupancy expense	15,735	14,846	14,608
Computer and equipment expense	9,793	9,768	9,591
Professional services expense	22,634	24,574	21,768
FDIC and State assessments	8,796	7,351	8,339
Marketing expense	4,126	3,403	4,607
Other real estate owned (income)/expense	(1,304)	(235)	15,116
Operations of investments in affordable housing	6,990	7,253	6,306
Amortization of core deposit premium	719	4,533	5,663
Cost associated with debt redemption	3,348	22,557	12,120
Other operating expense	13,583	11,507	16,094
Total non-interest expense	174,313	193,833	192,589
Income before income tax expense	219,795	194,170	184,171
Income tax expense	81,965	70,435	66,128
Net income	137,830	123,735	118,043
Less: net income attributable to noncontrolling interest		592	605
Net income attributable to Cathay General Bancorp	137,830	123,143	117,438
Dividends on preferred stock		(9,685)	(16,488)
Net income attributable to common stockholders	137,830	113,458	100,950
Other comprehensive income/(loss), net of tax:
Unrealized holding gains/(losses) on securities available for sale	30,468	(14,335)	19,645
Unrealized holding losses on cash flow hedge derivatives	(2,397)
Less: reclassification adjustment for gains included in net income	3,911	15,859	10,448
Total other comprehensive income/(loss), net of tax	24,160	(30,194)	9,197
Total comprehensive income	$ 161,990	$ 92,949	$ 126,635
Net income attributable to common stockholders per common share
Basic (in Dollars per share)	$ 1.73	$ 1.44	$ 1.28
Diluted (in Dollars per share)	$ 1.72	$ 1.43	$ 1.28
Basic average common shares outstanding (in Shares)	79,661,571	78,954,898	78,719,133
Diluted average common shares outstanding (in Shares)	80,106,895	79,137,983	78,723,297